staging: most: make functions static

split_arg_list() and audio_set_pcm_format() are being called from the
same file and is not referenced from outside, so make them as static.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>