mtd: ubi: wl: Fix a couple of kernel-doc issues

Fixes the following W=1 kernel build warning(s):

drivers/mtd/ubi/wl.c:584: warning: Function parameter or member 'nested' not described in 'schedule_erase'
drivers/mtd/ubi/wl.c:1075: warning: Excess function parameter 'shutdown' description in '__erase_worker'

Cc: Richard Weinberger <[e-mail]>
Cc: Miquel Raynal <[e-mail]>
Cc: Vignesh Raghavendra <[e-mail]>
Cc: [e-mail]
Signed-off-by: Lee Jones <[e-mail]>
Signed-off-by: Miquel Raynal <[e-mail]>
Link: https://lore.kernel.org/linux-mtd/[e-mail]

drivers/mtd/ubi/wl.c

···
  * @vol_id: the volume ID that last used this PEB
  * @lnum: the last used logical eraseblock number for the PEB
  * @torture: if the physical eraseblock has to be tortured
+ * @nested: denotes whether the work_sem is already held in read mode
  *
  * This function returns zero in case of success and a %-ENOMEM in case of
  * failure.
···
  * __erase_worker - physical eraseblock erase worker function.
  * @ubi: UBI device description object
  * @wl_wrk: the work object
- * @shutdown: non-zero if the worker has to free memory and exit
- * because the WL sub-system is shutting down
  *
  * This function erases a physical eraseblock and perform torture testing if
  * needed. It also takes care about marking the physical eraseblock bad if