media: davinci: fix two kernel-doc comments

A typo there is causing two warnings:
	drivers/media/platform/davinci/vpif_display.c:114: warning: Function parameter or member 'nplanes' not described in 'vpif_buffer_queue_setup'
	drivers/media/platform/davinci/vpif_capture.c:112: warning: Function parameter or member 'nplanes' not described in 'vpif_buffer_queue_setup'

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>