msm_serial_hs: Add ioctl support for UART Clock on/off request

This change adds support for ioctl implementation in HSUART
driver. UART Client application (e.g. Bluetooth) can make
request for UART Clock on/off using the ioctl mechanism.
UART Clock status also can be queried using this mechanism.

CRs-Fixed: 496245
Change-Id: I9531cf2f9eda487082b9719341c5ad84c15ad5f7
Signed-off-by: Saket Saurabh <ssaurabh@codeaurora.org>