lib/string: remove unnecessary #undefs

A few architecture specific string.h functions used to be implemented in
terms of preprocessor defines to the corresponding compiler builtins.
Since this is no longer the case, remove unused #undefs.

Only memcmp is still defined in terms of builtins for a few arches.

Link: https://github.com/ClangBuiltLinux/linux/issues/428
Link: https://lkml.kernel.org/r/20201120041113.89382-1-ndesaulniers@google.com
Fixes: 5f074f3e19 ("lib/string.c: implement a basic bcmp")
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Yury Norov <yury.norov@gmail.com>
Cc: Alexandru Ardelean <alexandru.ardelean@analog.com>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/string.c

@@ -85,7 +85,6 @@ EXPORT_SYMBOL(strcasecmp);
  * @dest: Where to copy the string to
  * @src: Where to copy the string from
  */
-#undef strcpy
 char *strcpy(char *dest, const char *src)
 {
 	char *tmp = dest;
@@ -302,7 +301,6 @@ EXPORT_SYMBOL(stpcpy);
  * @dest: The string to be appended to
  * @src: The string to append to it
  */
-#undef strcat
 char *strcat(char *dest, const char *src)
 {
 	char *tmp = dest;
@@ -378,7 +376,6 @@ EXPORT_SYMBOL(strlcat);
  * @cs: One string
  * @ct: Another string
  */
-#undef strcmp
 int strcmp(const char *cs, const char *ct)
 {
 	unsigned char c1, c2;
@@ -958,7 +955,6 @@ EXPORT_SYMBOL(memcmp);
  * while this particular implementation is a simple (tail) call to memcmp, do
  * not rely on anything but whether the return value is zero or non-zero.
  */
-#undef bcmp
 int bcmp(const void *a, const void *b, size_t len)
 {
 	return memcmp(a, b, len);