efi_selftest: efi_st_memcmp should return 0

If the compared memory areas match the return value should be 0.
We should not use the unrelated constant EFI_ST_SUCCESS.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>

lib/efi_selftest/efi_selftest_util.c

@@ -21,5 +21,5 @@ int efi_st_memcmp(const void *buf1, const void *buf2, size_t length)
 		++pos1;
 		++pos2;
 	}
-	return EFI_ST_SUCCESS;
+	return 0;
 }