msm: ipa3: map ipa-uc doorbell to PCIE-SMMU-CB for RNDIS direct flowcontrol

Map the ipa-uc flow-control doorbell to the
PCIE-SMMU-CB for TN A7 to be able to access
the Doorbell on APQ side and put in reserved2
channel scratch.

Change-Id: I3b1ffa5770d9579b1dc0ec3b04774fcf0d530921
Signed-off-by: Michael Adisumarta <madisuma@codeaurora.org>