ALSA: usb-audio: Apply 48kHz fixed rate playback for Jabra Evolve 65 headset

Jabra Evolve 65 headset appears as if supporting lower rates than
48kHz, but it actually doesn't work but with 48kHz for playback.

This patch applies a workaround to enforce the 48kHz like LINE6
devices already did.  The workaround is put in a unified helper
function, set_fixed_rate(), to be called from both places now.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206149
Link: https://lore.kernel.org/r/20200211111419.5895-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>