ASoC: wcd9320: Set HPH bias currents to low power mode

Setup the headphone path PA and DAC bias currents to low power
mode to increase power consumption efficiency

CRs-fixed: 485961
Change-Id: I9492e70f404f96502c7283b38f0d1f3738647d4c
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>