usb: gadget: prevent sending packets to IPA when in suspend

Adds support for querying the IPA RM status before calling
ipa_tx_dp(), in order to avoid sending data to the IPA
when it is unclocked.

Change-Id: I8261e53de774099062972fbdd496d42cba8140f8
Signed-off-by: Bar Weiner <bweiner@codeaurora.org>