ARM: dts: 8916: Add 200us delay to allow buck decay time.

Decrease the buck turn off delay to 200us as it is working for both
stability test cases and power dashboard use cases.

CRs-fixed: 682592
Change-Id: Ie6e3a6ea41f1825350eaea630f90f691651a0070
Signed-off-by: Anji Jonnala <anjir@codeaurora.org>