efi: libstub: Use local strncmp() implementation unconditionally

In preparation for moving the EFI stub functionality into the zboot
decompressor, switch to the stub's implementation of strncmp()
unconditionally.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

arch/arm64/kernel/image-vars.h

@@ -26,7 +26,6 @@ PROVIDE(__efistub_memchr		= __pi_memchr);
 PROVIDE(__efistub_strlen		= __pi_strlen);
 PROVIDE(__efistub_strnlen		= __pi_strnlen);
 PROVIDE(__efistub_strcmp		= __pi_strcmp);
-PROVIDE(__efistub_strncmp		= __pi_strncmp);
 PROVIDE(__efistub_strrchr		= __pi_strrchr);
 PROVIDE(__efistub_dcache_clean_poc	= __pi_dcache_clean_poc);
 

arch/riscv/kernel/image-vars.h

@@ -28,7 +28,6 @@ __efistub_memchr		= memchr;
 __efistub_strlen		= strlen;
 __efistub_strnlen		= strnlen;
 __efistub_strcmp		= strcmp;
-__efistub_strncmp		= strncmp;
 __efistub_strrchr		= strrchr;
 
 __efistub__start		= _start;

drivers/firmware/efi/libstub/string.c

@@ -35,7 +35,6 @@ char *strstr(const char *s1, const char *s2)
 }
 #endif
 
-#ifndef __HAVE_ARCH_STRNCMP
 /**
  * strncmp - Compare two length-limited strings
  * @cs: One string
@@ -57,7 +56,6 @@ int strncmp(const char *cs, const char *ct, size_t count)
 	}
 	return 0;
 }
-#endif
 
 /* Works only for digits and letters, but small and fast */
 #define TOLOWER(x) ((x) | 0x20)