ASoC: wcd9310: reduce mbhc button release GPIO debounce time

Current GPIO debounce time is too long so it delays next button
press detection.  Reduce this debounce time so driver can detect
next button press and release quickly.
Typically mic voltage ramps up within few milliseconds after button
release so 50ms is long enough.

Change-Id: I41e1e55f9393686b5c64074fcf14012e99b13e4b
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>