drivers: shs: Handle packets before init

Previously if there was a spurious packet before
shs init was completed an un-initialized spinlock
would cause a splat. This fix initializes spinlock
and correctly passes through packets received before
shs init is complete.

CRs-fixed: 2335316
Change-Id: I696067c31666ed9e57bfc802a6bf4878fa036bbe
Acked-by: Mahadevan Appadurai <mappadur@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>