mtd: Add flag to indicate panic_write

Added a flag to indicate a panic_write so that low level drivers can
use it to take required action where applicable, to ensure oops data
gets written to assigned mtd device.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/mtdcore.c

@@ -1124,6 +1124,9 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 		return -EROFS;
 	if (!len)
 		return 0;
+	if (!mtd->oops_panic_write)
+		mtd->oops_panic_write = true;
+
 	return mtd->_panic_write(mtd, to, len, retlen, buf);
 }
 EXPORT_SYMBOL_GPL(mtd_panic_write);