USB: f_audio_source: Remove pm_qos request under non atomic context

Currently driver is removing pm_qos request after acquiring spinlock in
pcm_close() callback. This could cause warning as pm_qos_remove_request()
can sleep. Hence move removing pm_qos request before acquiring spin lock.

Change-Id: I8e898934c4e83b80c994b2a293abbd920589ac62
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>