treewide: Replace CONFIG(ARCH_xx) tests

Once we support building stages for different architectures,
such CONFIG(ARCH_xx) tests do not evaluate correctly anymore.

Change-Id: I599995b3ed5c4dfd578c87067fe8bfc8c75b9d43
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42183
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/elog/elog.c

@@ -748,7 +748,7 @@ static bool elog_do_add_boot_count(void)
 /* Check and log POST codes from previous boot */
 static void log_last_boot_post(void)
 {
-#if CONFIG(ARCH_X86)
+#if ENV_X86
 	u8 code;
 	u32 extra;