Thumb-2: Add macros for the unified assembler syntax

This patch adds various C and assembler macros that help with using
the unified assembler syntax for compiling files to either ARM or
Thumb-2 modes.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index aef63c8..da28e7b 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -983,6 +983,9 @@
 	default AT91_TIMER_HZ if ARCH_AT91
 	default 100
 
+config ARM_ASM_UNIFIED
+	bool
+
 config AEABI
 	bool "Use the ARM EABI to compile the kernel"
 	help