greybus: svc watchdog: Disable watchdog upon entering suspend

SVC watchdog should be disabled when device is entering suspend mode.

Testing done:
 - Sanity tested on EVT1.5
 - Check no SVC ping during the suspend process
 - Check SVC watchdog is back on pinging once device is resumed

Signed-off-by: David Lin <dtwlin@google.com>
Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
[vaibhav.hiremath@linaro.org: Removed unwanted check in notifier callback and
Updated commit description]
Tested-by: Sandeep Patil <sspatil@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>