ASoC: wcd-spi: fix clock disable

Currently, the clock request is performed during init and the clock
is kept on assuming that there will be code download event followed
by init. This assumption may not always be true and might cause the
clock to be enabled when it is really not needed. Change fixes clock
disable such that clock is disabled right after init and re-enabled
again if code download event is raised.

CRs-fixed: 1071949
Change-Id: Icc415e911653012726e5b81b4fc09199560d5691
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>