boot: don't print error if device tree fixup protocol isn't supported

This isn't a failure we care about, and it's somewhat alarming to see a
red error message flash up on the display when booting, so this just
simply returns EFI_SUCCESS and skips printing the "error" altogether.

src/boot/efi/devicetree.c

@@ -33,8 +33,9 @@ static EFI_STATUS devicetree_fixup(struct devicetree_state *state, size_t len) {
         assert(state);
 
         err = BS->LocateProtocol(MAKE_GUID_PTR(EFI_DT_FIXUP_PROTOCOL), NULL, (void **) &fixup);
+        /* Skip fixup if we cannot locate device tree fixup protocol */
         if (err != EFI_SUCCESS)
-                return log_error_status(EFI_SUCCESS, "Could not locate device tree fixup protocol, skipping.");
+                return EFI_SUCCESS;
 
         size = devicetree_allocated(state);
         err = fixup->Fixup(fixup, PHYSICAL_ADDRESS_TO_POINTER(state->addr), &size,