bus: mhi: host: Optimize and update MMIO register write method

As of now, MMIO writes done after ready state transition use the
mhi_write_reg_field() API even though the whole register is being
written in most cases. Optimize this process by using mhi_write_reg()
API instead for those writes and use the mhi_write_reg_field()
API for MHI config registers only.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/1650304226-11080-3-git-send-email-quic_jhugo@quicinc.com


Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>