soc: qcom: ipa: fetch IPA context pointer in suspend/resume

Get the IPA context from the device, rather than using the global
ipa_ctx, in ipa_ap_suspend() and ipa_ap_resume().  Rename these
functions ipa_suspend() and ipa_resume().

Similarly, rename rmnet_ipa_ap_suspend() and rmnet_ipa_ap_resume()
to be rmnet_ipa_suspend() and rmnet_ipa_resume().

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