media: atomisp: Replace atomisp_drvfs attr with using driver.dev_groups attr

media: atomisp: Replace atomisp_drvfs attr with using driver.dev_groups attr

sysfs attributes preferably should not be manually be registered but
instead the driver.groups / driver.dev_groups driver struct members
should be used to have the driver core handle this in a race free
manner.

Using driver.groups would be the most direct replacement for
driver_[add|remove]_file, but some of the attributes actually need access
to the struct atomisp_device (*), so as part of modernizing this part of
the atomisp driver this change also makes the sysfs attribute device
attributes instead of driver attributes.

*) Before this change accessing these attributes without the driver having
bound would result in a NULL pointer deref, this commit fixes this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>