[STRING]: Move strcasecmp/strncasecmp to lib/string.c

We have several platforms using local copies of identical
code.

Signed-off-by: David S. Miller <davem@davemloft.net>

include/asm-sh/string.h

@@ -126,9 +126,6 @@ extern void *memchr(const void *__s, int __c, size_t __n);
 #define __HAVE_ARCH_STRLEN
 extern size_t strlen(const char *);
 
-/* arch/sh/lib/strcasecmp.c */
-extern int strcasecmp(const char *, const char *);
-
 #endif /* __KERNEL__ */
 
 #endif /* __ASM_SH_STRING_H */