ASoC: wcd: Depend on right config option

Kconfig doesn't have the CONFIG_ part of the option, so don't use
it here. This fixes a kconfig warning about missing a dependency
for "CONFIG_SPI" which doesn't exist because it's supposed to be
"SPI".

Change-Id: Ie449ff250dd87b0a445d34ee079082c6e91f147c
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>