asoc: wcd934x: set bus down flag right when notification reaches

Set bus_down_in_recovery flag as soon as possible when
BUS down notification reaches codec driver. This is to
avoid any unwanted slimbus transaction while BUS is still
not recovered.

Change-Id: I77917975372bf51e6aa881cbfc63c479478db375
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>