m68k: Uninline strchr()

Some versions of gcc replace calls to strstr() with single-character
"needle" string parameters by calls to strchr() behind our back.

If strchr() is defined as an inline function, this causes linking errors
like

	ERROR: "strchr" [drivers/target/target_core_mod.ko] undefined!

As m68k is the only architecture that has an inline strchr() and this
inline version is not an optimized asm version, uninline strchr() and use
the standard out-of-line C version in lib/string.c instead.

This also decreases the defconfig/allmodconfig kernel image sizes by a few
hundred bytes.
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/include/asm/string.h

@@ -81,18 +81,6 @@ static inline char *strncpy(char *dest, const char *src, size_t n)
 	strcpy(__d + strlen(__d), (s));		\
 })
 
-#define __HAVE_ARCH_STRCHR
-static inline char *strchr(const char *s, int c)
-{
-	char sc, ch = c;
-
-	for (; (sc = *s++) != ch; ) {
-		if (!sc)
-			return NULL;
-	}
-	return (char *)s - 1;
-}
-
 #ifndef CONFIG_COLDFIRE
 #define __HAVE_ARCH_STRCMP
 static inline int strcmp(const char *cs, const char *ct)