staging: bcm2835-camera: Remove check of the number of buffers supplied

Before 93841670 there was a need to ensure that there were sufficient
buffers supplied from the user to cover those being sent to the VPU
(always 1).
With 93841670 the buffers are linked 1:1 between MMAL and V4L2,
therefore there is no need for that check, and indeed it is wrong
as there is no need to submit all the buffers before starting streaming.

Fixes: 93841670 "staging: bcm2835-camera: Remove V4L2/MMAL buffer remapping"

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>