add the alsa driver from the latest RTSDK Signed-off-by: John Crispin <blogic@openwrt.org> Backport of r47205 SVN-Revision: 47230
add the alsa driver from the latest RTSDK Signed-off-by: John Crispin <blogic@openwrt.org> Backport of r47205 SVN-Revision: 47230