drivers: gnss: Add SiRFStarV GNSS boot mode functionality

BugLink: https://bugs.launchpad.net/bugs/1931727



Boot mode functionality needs to be enabled in SiRFStarV GNSS
chip to move the device to boot mode for automatic firmware
upgrade.

Change-Id: I00f51c56d29d19eb1789239778f8edd840b2b33f
Signed-off-by: Madhanraj Chelladurai <mchellad@codeaurora.org>
(cherry picked from commit 8102418fde0282e1b2f0b9a1b40786b0dcbc5933)
Signed-off-by: Shrirang Bagul <shrirang.bagul@canonical.com>