The cal_camerarx_create() function allocates resources with devm_*, and
thus doesn't need any manual cleanup. Those won't hold true for long, as
we will need to store resources that have no devm_* allocation variant
in cal_camerarx. Furthermore, devm_kzalloc() is the wrong memory
allocation API for structures that can be accessed from userspace, as
device nodes can be kept open across device removal.

Add a cal_camerarx_destroy() function to destroy a CAMERARX instance
explicitly, and switch to kzalloc() for memory allocation.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>