ASoC: msm: return the latest app type cfg data set when get is called

It is uncommon behavior to expect the caller of a get mixer control
to specify information. Return the last configuration information set
for the mixer control instead of expecting the caller to specify a
backend ID to get configuration information for.

CRs-Fixed: 2031732
Signed-off-by: Siena Richard <sienar@codeaurora.org>
Change-Id: Id1a5fd3e2cf9b7282df916c3973249137efde8c5