alsaloop: Support "Playback Pitch 1000000" rate shift

alsaloop: Support "Playback Pitch 1000000" rate shift

Linux 5.15 will introduce a new control element "Playback Pitch 1000000"
(commit 6fec018 ("usb: gadget: u_audio.c: Adding Playback Pitch ctl for
sync playback") which provides feedback mechanism for playback direction
of USB Audio Gadget. The control operates in the same way as the
existing control element "Capture Pitch 1000000".

This patch adds support for this feature.

Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>