powerpc/64s: Use symbolic macros for function entry encoding

In ppc_function_entry() we look for a specific set of instructions by
masking the instructions and comparing with a known value. Currently
those known values are just literal hex values, and we recently
discovered one of them was wrong.

Instead construct the values using the existing constants we have for
defining various fields of instructions.

Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Link: https://lore.kernel.org/r/20210309071544.515303-1-mpe@ellerman.id.au

arch/powerpc/include/asm/code-patching.h

@@ -73,9 +73,10 @@ void __patch_exception(int exc, unsigned long addr);
 #endif
 
 #define OP_RT_RA_MASK	0xffff0000UL
-#define LIS_R2		0x3c400000UL
-#define ADDIS_R2_R12	0x3c4c0000UL
-#define ADDI_R2_R2	0x38420000UL
+#define LIS_R2		(PPC_INST_ADDIS | __PPC_RT(R2))
+#define ADDIS_R2_R12	(PPC_INST_ADDIS | __PPC_RT(R2) | __PPC_RA(R12))
+#define ADDI_R2_R2	(PPC_INST_ADDI  | __PPC_RT(R2) | __PPC_RA(R2))
+
 
 static inline unsigned long ppc_function_entry(void *func)
 {