powerpc/inst: Refactor ___get_user_instr()

PPC64 version of ___get_user_instr() can be used for PPC32 as well,
by simply disabling the suffix part with IS_ENABLED(CONFIG_PPC64).
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1f0ede830ccb33a659119a55cb590820c27004db.1638208156.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/inst.h

@@ -4,8 +4,6 @@
 
 #include <asm/ppc-opcode.h>
 
-#ifdef CONFIG_PPC64
-
 #define ___get_user_instr(gu_op, dest, ptr)				\
 ({									\
 	long __gui_ret;							\
@@ -16,7 +14,7 @@
 	__chk_user_ptr(ptr);						\
 	__gui_ret = gu_op(__prefix, __gui_ptr);				\
 	if (__gui_ret == 0) {						\
-		if ((__prefix >> 26) == OP_PREFIX) {			\
+		if (IS_ENABLED(CONFIG_PPC64) && (__prefix >> 26) == OP_PREFIX) { \
 			__gui_ret = gu_op(__suffix, __gui_ptr + 1);	\
 			__gui_inst = ppc_inst_prefix(__prefix, __suffix); \
 		} else {						\
@@ -27,13 +25,6 @@
 	}								\
 	__gui_ret;							\
 })
-#else /* !CONFIG_PPC64 */
-#define ___get_user_instr(gu_op, dest, ptr)				\
-({									\
-	__chk_user_ptr(ptr);						\
-	gu_op((dest).val, (u32 __user *)(ptr));				\
-})
-#endif /* CONFIG_PPC64 */
 
 #define get_user_instr(x, ptr) ___get_user_instr(get_user, x, ptr)
 
@@ -71,7 +62,7 @@ static inline u32 ppc_inst_suffix(struct ppc_inst x)
 }
 
 #else
-#define ppc_inst_prefix(x, y) ppc_inst(x)
+#define ppc_inst_prefix(x, y) ((void)y, ppc_inst(x))
 
 static inline u32 ppc_inst_suffix(struct ppc_inst x)
 {