media: staging: media: imx: imx7-mipi-csis: Dump MIPI_CSIS_FRAME_COUNTER_CH0 register

The frame counter is useful debugging information, add it to the
register dump printed by mipi_csis_dump_regs().

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Tested-by: Jerome Brunet <jbrunet@baylibre.com> # On i.MX8MP
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>