soc: qcom: bgdaemon: Add support for BG soft reset on Modem down

When Modem goes down, to re-establish the connections, BG-Daemon
toggles the bg-reset gpio to reset BG.

Change-Id: Idb319fb157e04c78a7db207fa450e5930c1e6dd8
Signed-off-by: Arjun Singh <arsingh@codeaurora.org>