oss4: also accept formats not natively supported

oss4: also accept formats not natively supported

Also accept formats that are not natively supported by the
hardware, OSS4 can convert them internally. List the native
formats first in the caps though, to express our preference
for the native formats. We need this in order to support the
case properly where the audio hardware supports only e.g.
little endian PCM, but the host is big endian, since many
audio elements only support native endianness and make the
reasonable assumption that any audiosink will be able to
handle audio in native endianness.

Based on patch by Jerry Tan <jerry.tan@sun.com>

Fixes #614317.