media: intel/ipu6: fix the buffer flags caused by wrong parentheses

The buffer flags is set by wrong due to wrong parentheses, the
FL_INCOMING flag is never taken an account.
Fix it by wrapping the ternary conditional operation with parentheses.

Fixes: 3c1dfb5a ("media: intel/ipu6: input system video nodes and buffer queues")
Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>