qemu: MULTI_CONSOLE_API=0 causes build error

Add crash_console_init declaration to console.h
Only enable MULTI_CONSOLE_API for AArch64

Fixes ARM-software/tf-issues#571

Signed-off-by: Michalis Pappas <mpappas@fastmail.fm>
diff --git a/plat/qemu/platform.mk b/plat/qemu/platform.mk
index a9fbcd7..017807b 100644
--- a/plat/qemu/platform.mk
+++ b/plat/qemu/platform.mk
@@ -169,7 +169,12 @@
 endif
 
 SEPARATE_CODE_AND_RODATA := 1
-MULTI_CONSOLE_API	 := 1
+
+# Use MULTI_CONSOLE_API by default only on AArch64
+# as it is not yet supported on AArch32
+ifeq ($(ARCH),aarch64)
+MULTI_CONSOLE_API	:= 1
+endif
 
 # Disable the PSCI platform compatibility layer
 ENABLE_PLAT_COMPAT	:= 	0