ASoC: bolero: Resolve handset record not resuming after PDR

Handset record does not resume if pdr is performed
during record. Make VA DMIC_CTL registers as volatile
to write proper value of register to hw.

Change-Id: I2cc10d2eab18e3e8126c56caffa126195c02b4e3
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>