x86/boot/string: Add missing function prototypes

Silence "warning: no previous prototype for ... [-Wmissing-prototypes]"
warnings from string.h when building under W=1.

 [ bp: Clarify commit message. ]
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211119175325.3668419-1-keescook@chromium.org

arch/x86/boot/string.h

@@ -8,8 +8,10 @@
 #undef memcmp
 
 void *memcpy(void *dst, const void *src, size_t len);
+void *memmove(void *dst, const void *src, size_t len);
 void *memset(void *dst, int c, size_t len);
 int memcmp(const void *s1, const void *s2, size_t len);
+int bcmp(const void *s1, const void *s2, size_t len);
 
 /* Access builtin version by default. */
 #define memcpy(d,s,l) __builtin_memcpy(d,s,l)
@@ -25,6 +27,7 @@ extern size_t strnlen(const char *s, size_t maxlen);
 extern unsigned int atou(const char *s);
 extern unsigned long long simple_strtoull(const char *cp, char **endp,
 					  unsigned int base);
+long simple_strtol(const char *cp, char **endp, unsigned int base);
 
 int kstrtoull(const char *s, unsigned int base, unsigned long long *res);
 int boot_kstrtoul(const char *s, unsigned int base, unsigned long *res);