AArch32: Add assembly helpers

This patch adds various assembly helpers for AArch32 like :

* cache management : Functions to flush, invalidate and clean
cache by MVA. Also helpers to do cache operations by set-way
are also added.

* stack management: Macros to declare stack and get the current
stack corresponding to current CPU.

* Misc: Macros to access co processor registers in AArch32,
macros to define functions in assembly, assert macros, generic
`do_panic()` implementation and function to zero block of memory.

Change-Id: I7b78ca3f922c0eda39beb9786b7150e9193425be
diff --git a/lib/aarch32/misc_helpers.S b/lib/aarch32/misc_helpers.S
new file mode 100644
index 0000000..63ac1a7
--- /dev/null
+++ b/lib/aarch32/misc_helpers.S
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <arch.h>
+#include <asm_macros.S>
+#include <assert_macros.S>
+
+	.globl	zeromem
+
+/* -----------------------------------------------------------------------
+ * void zeromem(void *mem, unsigned int length);
+ *
+ * Initialise a memory region to 0.
+ * The memory address and length must be 4-byte aligned.
+ * -----------------------------------------------------------------------
+ */
+func zeromem
+#if ASM_ASSERTION
+	tst	r0, #0x3
+	ASM_ASSERT(eq)
+	tst	r1, #0x3
+	ASM_ASSERT(eq)
+#endif
+	add	r2, r0, r1
+	mov	r1, #0
+z_loop:
+	cmp	r2, r0
+	beq	z_end
+	str	r1, [r0], #4
+	b	z_loop
+z_end:
+	bx	lr
+endfunc zeromem