ASoC: wcd9310: Don't request irq until MBHC is fully configured

There is a chance that MBHC irq is requested even before MBHC isn't fully
configured when ACDB calibration data is downloaded from file system.
Make sure to request irq after configuring MBHC to avoid unwanted early
irq.  If interrupt asserts too early, divide by zero exception can occur
during voltage calculation.

CRs-fixed: 363895
Change-Id: Ib7aecfe5892043d797aafbef49da617edc7ac205
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>