rsi: disable fw watchdog timer during reset

Firmware's watchdog timer should be disabled as a part of reset
sequence. This change fixes a firmware hang issue observed during
stress tests.

Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Siva Rebbagondla <siva.rebbagondla@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>