msm : Add support to get user defined TTY device for Uart port

Currently UART port is enumerating with platform device ID. It is not
necessary that TTY<ID> is same as available UART device ID. Provide
optional support which allows to override used platform device ID with
uart port by userid to get TTY based Uart device as /dev/ttyHS<userid>
instead of /dev/ttyHS<ID>.This support helps third party application/test
framework to use the same TTY uart device name across different platform
without changing in those applications as it is not necessary that on
different platform used UART device would be having same TTY<ID> name.
The userid value should be from 0 to 256

CRs-Fixed: 386736
Signed-off-by: Saket Saurabh <ssaurabh@codeaurora.org>
(cherry picked from commit 51690e5e)

Change-Id: I3d9546ceab48345d0e3456c6223e3ff82e5a2f8b
Signed-off-by: Sudhir Sharma <sudsha@codeaurora.org>