The style of this driver uses periods at the end of sentences in
comments, but it is applied inconsitently.

Update a selection of comments which were discovered to be missing their
period. Also fix the spelling of one usage of 'instantiate'
Signed-off-by: NKieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab+samsung@kernel.org>