media: imx-pxp: Check for pxp_soft_reset() error

pxp_soft_reset() may fail with a timeout, so it is better to propagate
the error in this case.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>