[PATCH] powerpc: Quick fix upstream main line build error on PowerPC

[Dongsheng Wang <dongsheng.wang@freescale.com>]

From: Wang Dongsheng <dongsheng.wang@freescale.com>

This issue caused on 'commit 990486c8af04 ("strscpy: zero any trailing
garbage bytes in the destination")'.

zero_bytemask is not implemented on PowerPC. So copy the zero_bytemask
of BIG_ENDIAN implementation from include/asm-generic/word-at-a-time.h
to arch/powerpc/include/asm/word-at-a-time.h.

Build message:
lib/string.c: In function 'strscpy':
lib/string.c:209:4: error: implicit declaration of function
	'zero_bytemask' [-Werror=implicit-function-declaration]
	*(unsigned long *)(dest+res) = c & zero_bytemask(data);
cc1: some warnings being treated as errors
make[1]: *** [lib/string.o] Error 1
make[1]: *** Waiting for unfinished jobs....

Signed-off-by: Wang Dongsheng <dongsheng.wang@freescale.com>

diff --git a/arch/powerpc/include/asm/word-at-a-time.h b/arch/powerpc/include/asm/word-at-a-time.h
index 5b3a903..d891456 100644
--- a/arch/powerpc/include/asm/word-at-a-time.h
+++ b/arch/powerpc/include/asm/word-at-a-time.h
@@ -40,6 +40,10 @@ static inline bool has_zero(unsigned long val, unsigned long *data, const struct
 	return (val + c->high_bits) & ~rhs;
 }
 
+#ifndef zero_bytemask
+#define zero_bytemask(mask) (~1ul << __fls(mask))
+#endif
+
 #else
 
 #ifdef CONFIG_64BIT
-- 
2.1.0.27.g96db324