ARM: dts: msm: Enable Haptics during TWM entry for SDM429w + BG

BG controls haptics in TWM mode via ext pwm pin. Add property to
enable configuration of haptics in ext-pin pwm mode from HLOS
while entering TWM mode.

Change-Id: Ief335f6a16e45cd27fc504ad37c82861e7e696bf
Signed-off-by: Umang Chheda <uchheda@codeaurora.org>