icnss: Avoid power-off if driver is registered

If driver is registered before FW ready indication then bus error
observed because of powering off the hardware before calling
driver probe. Fix the issue by powering off only when driver is
not registered.
Also add top level reset after FW ready without which bus error
is observed.

CRs-fixed: 1015484
Change-Id: I26609c4011f10c1a9ee62b092050394e064ee2a2
Signed-off-by: Prashanth Bhatta <bhattap@codeaurora.org>