mtd: mtdoops: Fix kmsgdump parameter renaming.

When the kmsg_dumper callback parameter changed, the reason variable
in mtdoops_do_dump() was not updated accordingly.
This breaks the build with mtdoops.

Fixes: e1a261ba599e ("printk: Add a short description string to kmsg_dump()")
Suggested-by: Knop Ryszard <[e-mail]>
Signed-off-by: Jocelyn Falempe <[e-mail]>
Acked-by: Richard Weinberger <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/mtd/mtdoops.c

···
 	struct kmsg_dump_iter iter;
 
 	/* Only dump oopses if dump_oops is set */
-	if (reason == KMSG_DUMP_OOPS && !dump_oops)
+	if (detail->reason == KMSG_DUMP_OOPS && !dump_oops)
 		return;
 
 	kmsg_dump_rewind(&iter);
···
 			     record_size - sizeof(struct mtdoops_hdr), NULL);
 	clear_bit(0, &cxt->oops_buf_busy);
 
-	if (reason != KMSG_DUMP_OOPS) {
+	if (detail->reason != KMSG_DUMP_OOPS) {
 		/* Panics must be written immediately */
 		mtdoops_write(cxt, 1);
 	} else {