Support lib/zt_common.h to be used in assembler and add _AC macro

Support `lib/zt_common.h` to be used in assembler files. In addition,
add the macro `_AC` that can be used to make constant macros usable in
both assembler and C code.

Suggested-by: Philipp Rudo <prudo@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

include/lib/zt_common.h

@@ -15,6 +15,21 @@
 #define STRINGIFY_1(x)			#x
 #define STRINGIFY(x)			STRINGIFY_1(x)
 
+/* Use this macro to make constant macros usable in both assembler and
+ * C code.
+ *
+ * Usage example:
+ *  #define IMAGE_ENTRY _AC(0x10000, UL)
+ */
+#ifdef __ASSEMBLER__
+#define _AC(X, TYPE)	X
+#else
+#define _AC(X, TYPE)	X##TYPE
+#endif
+
+
+#ifndef __ASSEMBLER__
+
 #ifdef UNUSED
 #elif defined(__GNUC__)
 # define UNUSED(x) UNUSED_ ## x __attribute__((unused))
@@ -50,4 +65,5 @@ typedef signed short int	s16;
 typedef unsigned char		u8;
 typedef signed char		s8;
 
+#endif /* __ASSEMBLER__ */
 #endif /* LIB_ZT_COMMON_H */