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: I96056fc860c5be66e4b5bbdfecf6b572eaae971f
Signed-off-by: Naresh Munagala <nareshm@codeaurora.org>