serial: msm_serial_hs: Add snapshot of serial highspeed driver

These changes adds a snapshot of the BLSP based HSUART driver from
the 4.4 branch.
kernel-4.4 baseline: 'e29d253ecf048
("msm: mdss: dsi: Remove redundant opmode configuration")'

Change-Id: Ieafcc94ba74e58333bd9d9e2ccb351e0d4fa94f6
Signed-off-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>