atomisp: fix potential NULL pointer dereferences

The asd pointer is used in lockdep_assert_held() before the check if
asd is NULL.

This fixes two smatch warnings:

drivers/staging/media/atomisp/pci/atomisp_cmd.c:3697 atomisp_handle_parameter_and_buffer() warn: variable dereferenced before check 'asd' (see line 3695)
drivers/staging/media/atomisp/pci/atomisp_cmd.c:3779 atomisp_set_parameters() warn: variable dereferenced before check 'asd' (see line 3777)

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>