media: ti-vpe: cal: Remove unneeded phy->sensor NULL check

The phy->sensor NULL check in cal_camerarx_get_external_rate() is not
needed, as the V4L2 video devices are only registered when the sensor is
bound. Remove it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>