arm64/efi: Make strrchr() available to the EFI namespace

libfdt gained a new dependency on strrchr, so make it available to the
EFI namespace before we update libfdt.

Thanks to Ard for providing this fix.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>

arch/arm64/kernel/image.h

@@ -103,6 +103,7 @@ __efistub_strlen		= KALLSYMS_HIDE(__pi_strlen);
 __efistub_strnlen		= KALLSYMS_HIDE(__pi_strnlen);
 __efistub_strcmp		= KALLSYMS_HIDE(__pi_strcmp);
 __efistub_strncmp		= KALLSYMS_HIDE(__pi_strncmp);
+__efistub_strrchr		= KALLSYMS_HIDE(__pi_strrchr);
 __efistub___flush_dcache_area	= KALLSYMS_HIDE(__pi___flush_dcache_area);
 
 #ifdef CONFIG_KASAN

arch/arm64/lib/strrchr.S

@@ -40,4 +40,4 @@ ENTRY(strrchr)
 	b	1b
 2:	mov	x0, x3
 	ret
-ENDPROC(strrchr)
+ENDPIPROC(strrchr)