powerpc/signal: Use code patching instead of hardcoding

Instead of hardcoding code modifications, use code patching functions.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index a6e9e31..7f693e0 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -257,6 +257,7 @@
 #define PPC_INST_MTSPR_DSCR_USER_MASK	0xfc1ffffe
 #define PPC_INST_MFVSRD			0x7c000066
 #define PPC_INST_MTVSRD			0x7c000166
+#define PPC_INST_SC			0x44000002
 #define PPC_INST_SLBFEE			0x7c0007a7
 #define PPC_INST_SLBIA			0x7c0003e4