driver: soc: bgcom: Communicate with Blackghost over SPI

Black Ghost is a low powered chip connected to APSS. It runs at
low power. BGCOM APIs provides the interface to communicate with
blackghost over SPI. BGCOM handles the interrupt raised by Blackghost
and notify the G-linik about interrupt.

Change-Id: If2d048ea3d71efee930f9fc8bacced0703323929
Signed-off-by: Arjun Singh <arsingh@codeaurora.org>