ASoC: wcd-spi: Initialize local variables before usage

Initliaze the local variables that are used in functions to return
success or error codes. This fixes possible cases where undefined
error codes are returned.

CRs-Fixed: 1070186
Change-Id: I74bed6cfd9753765b15d17d69ba30f61875e87c8
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>