mfd: timpani-codec: Making AUXPGA gain register as uncacheable

AUXPGA LR gain register is treated as a cacheable with which the
register value is changed when device is opened twice. So making
the LR gain register as uncacheable which in turn apply the gain
value to the codec every time device is opened.

CRs-Fixed: 319366
Change-Id: Ibae39848bd05d8462e805cf79c352f2453dc86f4
Signed-off-by: Vinay Vaka <vvaka@codeaurora.org>