ASoC: msm8x16-wcd: update speaker path tear down sequence

Disable speaker boost at the beginning of the tear
down path so that the boost gets sufficient time
to settle down before the speaker pa is disabled
and update boost current limit to 1.5A.

CRs-Fixed: 748109
Change-Id: Ied757d6fa4d557a283f15a1dac0609af90168862
Signed-off-by: Aravind Kumar <akumark@codeaurora.org>