drivers: esoc: Do a warm reset as shutdown is not implemented

As shutdown is not implemented for kona, do a warm reset in
graceful shutdown and adb reboot scenarios. This should help
in resetting the modem state.

Change-Id: I5e59f3db12c34e8ad64e7ada989b9b1e54429566
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>