media: ov2740: Check hwcfg after allocating the ov2740 struct

Alloc ov2740_data and set up the drvdata pointer before calling
ov2740_check_hwcfg().

This is a preparation patch to allow ov2740_check_hwcfg()
to store some of the parsed data in the ov2740 struct.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>