media: stk1160: Use usb_endpoint_is_isoc_in() rather than duplicating its implementation

Reuse existing functionality from usb_endpoint_is_isoc_in() instead of
keeping duplicate source code.

The source code was transformed by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>