soc: qcom: ipa: pass an IPA pointer to ipa_process_interrupts()

Pass an IPA pointer to ipa_process_interrupts() so it can be used
(eventually, by called functions) instead of the global IPA context.
Similarly, add an IPA pointer argument to ipa_handle_interrupt(),
and to ipa_tx_suspend_interrupt_wa().

Signed-off-by: Alex Elder <elder@linaro.org>