wlcore: add debugfs control over rx interrupt pacing

Add control over several conf fields which combined
control the rx interrupt pacing mechanism, that is avoiding
getting an interrupt following a single frame rx but instead
have the FW trigger the interrupt only after a certain
amount of frames received or a timeout.

Signed-off-by: Eyal Shapira <eyal@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>