arm64: klib: Optimised string functions

This patch introduces AArch64-specific string functions (strchr,
strrchr).

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/include/asm/string.h b/arch/arm64/include/asm/string.h
index be8a644..3ee8b30 100644
--- a/arch/arm64/include/asm/string.h
+++ b/arch/arm64/include/asm/string.h
@@ -16,6 +16,12 @@
 #ifndef __ASM_STRING_H
 #define __ASM_STRING_H
 
+#define __HAVE_ARCH_STRRCHR
+extern char *strrchr(const char *, int c);
+
+#define __HAVE_ARCH_STRCHR
+extern char *strchr(const char *, int c);
+
 #define __HAVE_ARCH_MEMCPY
 extern void *memcpy(void *, const void *, __kernel_size_t);