Remove build option `ASM_ASSERTION`

The build option `ENABLE_ASSERTIONS` should be used instead. That way
both C and ASM assertions can be enabled or disabled together.

All occurrences of `ASM_ASSERTION` in common code and ARM platforms have
been replaced by `ENABLE_ASSERTIONS`.

ASM_ASSERTION has been removed from the user guide.

Change-Id: I51f1991f11b9b7ff83e787c9a3270c274748ec6f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/lib/cpus/aarch64/cpu_helpers.S b/lib/cpus/aarch64/cpu_helpers.S
index 47cb6a2..6a39916 100644
--- a/lib/cpus/aarch64/cpu_helpers.S
+++ b/lib/cpus/aarch64/cpu_helpers.S
@@ -55,7 +55,7 @@
 
 	/* Get the matching cpu_ops pointer */
 	bl	get_cpu_ops_ptr
-#if ASM_ASSERTION
+#if ENABLE_ASSERTIONS
 	cmp	x0, #0
 	ASM_ASSERT(ne)
 #endif
@@ -94,7 +94,7 @@
 
 	mrs	x1, tpidr_el3
 	ldr	x0, [x1, #CPU_DATA_CPU_OPS_PTR]
-#if ASM_ASSERTION
+#if ENABLE_ASSERTIONS
 	cmp	x0, #0
 	ASM_ASSERT(ne)
 #endif
@@ -120,7 +120,7 @@
 	cbnz	x0, 1f
 	mov	x10, x30
 	bl	get_cpu_ops_ptr
-#if ASM_ASSERTION
+#if ENABLE_ASSERTIONS
 	cmp	x0, #0
 	ASM_ASSERT(ne)
 #endif