drivers/mrc_cache: Reduce severity of `region not found` log message

On autogenerated FMAPs, there's no `UNIFIED_MRC_CACHE` region. The
current code will print a spurious error message about it, though.

Reduce the log level to BIOS_INFO to avoid confusion.

Change-Id: I0961bb2a7d2d81dc5c0d28f6e6c29b320421fc3e
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45076
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Christian Walter <christian.walter@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/mrc_cache/mrc_cache.c

@@ -480,7 +480,7 @@ static int protect_mrc_cache(const char *name)
 		return 0;
 
 	if (lookup_region_by_name(name, &region) < 0) {
-		printk(BIOS_ERR, "MRC: Could not find region '%s'\n", name);
+		printk(BIOS_INFO, "MRC: Could not find region '%s'\n", name);
 		return -1;
 	}