dwc3-msm: Readback USB GSI wrapper register after updating

In some of cases, it has been observed that USB GSI wrapper
is trying to access IPA GSI doorbell register which is pending
at bus level whereas USB software has detached SMMU and power
collapse controller. This results into global SMMU page fault.
Fix this issue by reading back USB GSI wrapper register after
updating it to make sure that register write has not buffered
at bus level or cache level. To achieve this, remove
dwc3_msm_write_readback() API usage, readback updated register
with dwc3_msm_write_reg_field() API and replace references of
dwc3_msm_write_readback() API.

Change-Id: Ib77e23d3430cb69a47478618d79851acea5c3c56
Signed-off-by: Mayank Rana <mrana@codeaurora.org>
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>