ASoC: wcd937x: Reduce latency in case of impedance detection

Bulk read api does not work properly for swr regmap,
causing failure/delay in impedance detection.
Use regmap read api to avoid the issue.

CRs-Fixed: 2301798
Change-Id: I5727cfcb7846f40f5b0f75b7976b492e2a2bfde0
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>