mtd: rawnand: meson: only initialize the RB completion once

Documentation/scheduler/completion.txt states:
  Calling init_completion() on the same completion object twice is
  most likely a bug as it re-initializes the queue to an empty queue and
  enqueued tasks could get "lost" - use reinit_completion() in that case,
  but be aware of other races.

Initialize nfc->completion in meson_nfc_probe using init_completion and
change the call in meson_nfc_queue_rb to reinit_completion so the logic
matches what the documentation suggests.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Liang Yang <liang.yang@amlogic.com>
Acked-by: Liang Yang <liang.yang@amlogic.com>
Tested-by: Liang Yang <liang.yang@amlogic.com>
Acked-by: Liang Yang <liang.yang@amlogic.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>