BugLink: https://bugs.launchpad.net/bugs/1855313

[ Upstream commit b95f83ab ]

The MTD device reference is dropped via put_mtd_device, however its
field ->index is read and passed to ubi_msg. To fix this, the patch
moves the reference dropping after calling ubi_msg.
Signed-off-by: Pan Bian <bianpan2016@163.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>