msm: UIM driver msm_uim

UIM (User Identity Module) driver makes use of existing MSM serial
driver. It configures UIM clock during startup and shutdown of
UART device.

Change-Id: If1b249639e9969273882ad000ef9b1495b8c7013
Acked-by: Ho Lee <holee@qualcomm.com>
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>