v4l2: Incompatible pointer type compiler error on musl

The musl C library defines ioctl thusly:

int ioctl (int, int, ...);

However, gstv4l2object.h defines GstV4l2Object's ioctl field as:

gint (*ioctl) (gint fd, ioctl_req_t request, ...);

and, except when __ANDROID__ is defined, gstv4l2object.h defines ioctl_req_t as a gulong.

This causes a warning when building gst-plugins-good against musl:

CC libgstvideo4linux2_la-gstv4l2object.lo gstv4l2object.c: In function 'gst_v4l2_object_new': gstv4l2object.c:532:23: error: assignment from incompatible pointer type [-Werror=incompatible-pointer-types] v4l2object->ioctl = ioctl; ^ cc1: all warnings being treated as errors

It looks like gstv4l2object.h