microblaze: Copy ppc asm-compat.h for clean handling of constants in asm and C

Provides the ASM_CONST macro for creating asm-safe constants.

No users yet, we'll be using it in upcoming page.h commit, for generating
the LOAD_OFFSET macro
Signed-off-by: John Williams <john.williams@petalogix.com>

arch/microblaze/include/asm/asm-compat.h

+#ifndef _ASM_MICROBLAZE_ASM_COMPAT_H
+#define _ASM_MICROBLAZE_ASM_COMPAT_H
+
+#include <asm/types.h>
+
+#ifdef __ASSEMBLY__
+#  define stringify_in_c(...)	__VA_ARGS__
+#  define ASM_CONST(x)		x
+#else
+/* This version of stringify will deal with commas... */
+#  define __stringify_in_c(...)	#__VA_ARGS__
+#  define stringify_in_c(...)	__stringify_in_c(__VA_ARGS__) " "
+#  define __ASM_CONST(x)	x##UL
+#  define ASM_CONST(x)		__ASM_CONST(x)
+#endif
+
+#endif /* _ASM_MICROBLAZE_ASM_COMPAT_H */