staging: atomisp: remove redudant condition in if-statement

The V4L2_FIELD_ANY is zero, so the (!field) is same meaning
with (field == V4L2_FIELD_ANY) in if-statement.

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>