msm_serial_hs_ti: Cleanup & add back comments

HTC is known for stripping all the comments in their kernels
Restored comments from msm_serial_hs based on 89443dc3f74ff0e45a4c1fee096d576a082bef69

Also added back some code to bring up-to-date with the original msm_serial_hs driver
msm_serial_hs_ti: Bring up-to-date with msm_serial_hs

Now that we know the differences between the TI & the generic driver,
updating is much easier