media: atomisp: Drop global atomisp_dev variable (easy cases)

Refactor code to avoid use of atomisp_dev global variable
where it's easy to achieve.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>