Move V4L feature declarations and DTrace provider definitions from
linux_common.c to linux_util.c so they become available on i386.

linux_common.c defines the linux_common kernel module but this module does
not exist on i386 and linux_common.c is not included in the linux module.
linux_util.c is included in the linux_common module on amd64 and the linux
module on i386.

Remove linux_common.c from files.i386 again. It was added recently in
r367433 when the DTrace provider definitions were moved.

The V4L feature declarations were moved to linux_common in r283423.