net: ipa: distinguish system from runtime suspend

Add a new flag that is set when the hardware is suspended due to a
system suspend operation, distingishing it from runtime suspend.
Use it in the SUSPEND IPA interrupt handler to determine whether to
trigger a system resume because of the event.  Define new suspend
and resume power management callback functions to set and clear the
new flag, respectively.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>