mtd: call external _get and _put in right order

MTD provider provides mtd_info object to mtd subsystem.
With kref patch the mtd_info object can be alive after
provider released mtd device.
Fix calling order in _get and _put functions to allow
mtd provider to safely alloc and release mtd object.

Execute:
1) call external _get
2) get_module
3) add internal kref
in the get function and opposite order in the put one.

The _put_device callback should be the last in put
as the master struct memory may be freed in this callback.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230620131905.648089-3-alexander.usyskin@intel.com