net: ipa: introduce ipa_endpoint_program_suspend()

Create a new helper function that encapsulates enabling or disabling
suspend on an RX endpoint.  It returns the previous state of the
endpoint (true means suspend mode was enabled).

Create another function that handles enabling or disabling delay mode
on a TX endpoint.  Delay mode does not work correctly on IPA version
4.2, so we don't currently use it (and shouldn't).

We only set delay mode in one case, and although we don't expect an
endpoint to already be in delay mode, it doesn't really matter if it
was.  So the delay function doesn't return a value.

Stop issuing warnings if the previous suspend or delay mode state
differs from what is expected.

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