powerpc: EX_TABLE macro for exception tables

This macro is taken from s390, and allows more flexibility in
changing exception table format.

mpe: Put it in ppc_asm.h and only define one version using
stringinfy_in_c(). Add some empty definitions and headers to keep the
selftests happy.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/sysdev/tsi108_pci.c b/arch/powerpc/sysdev/tsi108_pci.c
index 57c971b7..53a16aa 100644
--- a/arch/powerpc/sysdev/tsi108_pci.c
+++ b/arch/powerpc/sysdev/tsi108_pci.c
@@ -137,10 +137,8 @@ void tsi108_clear_pci_error(u32 pci_cfg_base)
 		".section .fixup,\"ax\"\n"		\
 		"3:	li %0,-1\n"			\
 		"	b 2b\n"				\
-		".section __ex_table,\"a\"\n"		\
-		"	.align 2\n"			\
-		"	.long 1b,3b\n"			\
-		".text"					\
+		".previous\n"				\
+		EX_TABLE(1b, 3b)			\
 		: "=r"(x) : "r"(addr))
 
 int