ARM: dts: msm: Enable bus suspend only for sm8150-sdx50m

Bus suspend is enabled by default on secondary usb port
for all sm8150 variants which is not required. Enable it
only for sm8150-sdx50m.

Change-Id: I11f0adde36ec2fd6d1d1c844243225a5bf813861
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>