mfd: wcd934x: Add additional interrupts required for MBHC support

WCD934x supports Multi Button Headset control which enable headset detection
along with headset button detection.

This patch adds interrupts required for MBHC functionality.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>