net: ipa: kill ipa_power_suspend_handler()

Now that ipa_power_suspend_handler() is a trivial wrapper around
ipa_interrupt_suspend_clear_all(), we can open-code it in the one
place it's used, and get rid of the function.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>