drivers: gnss: Add SiRFStart GNSS chip power controls

This is a driver to handle SiRFStar GNSS chip power controls,
a device node is created to interact with driver power controls
and exposes set of IOCTLs. These IOCTLs provide mechanisms to
transition of GNSS receiver power state.

Change-Id: Idf8ff2553736221930f4f032455692e3752176ce
Signed-off-by: Vijayakumar Badiger <vbadig@codeaurora.org>
Signed-off-by: Santoshkumar Zalake <szalake@codeaurora.org>