msm: ehci-hsic: Add support to disable internal clock gating

EHCI cores on latest MSMs have internal clock gating enabled
by default. Stability issues (random enumeration failures)
have been observed with some CORES where clock gating feature
doesn't work as expected. Provide a DT parameter that can be
used to disabled clock gating in hardware.

CRs-fixed: 538509
Change-Id: I1fcac505e4a240367e3a685b5e8c78f52fbb2f6a
Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>