msm: gsi: add support for GSI configuration and enablement

This will allow the entity in charge of loading the GSI FW
to perform required GSI core init configuration
(Can be done before/after the GSI FW has been loaded, but
before it is enabled).
as well as to enable it (Only after the FW has been loaded).

Change-Id: I894a42dfc35b56204c5339c2d5044e0e1930e1bc
Acked-by: David Arinzon <darinzon@qti.qualcomm.com>
Signed-off-by: Sivan Reinstein <sivanr@codeaurora.org>