msm: ipa: add ipa tethering stats support to IPA WAN driver

In tethering cases where IPA HW offloading is applied, it is required
from the IPA WAN driver to communicate with the IPA Q6 driver in order
to retrieve data usage statistics for the tethering pipes as well as
the network/quota usage on a specific PDN.

Change-Id: Iffc3ada159f85d6a5ddd21a444a6ad7563e725e9
Acked-by: David Arinzon <darinzon@qti.qualcomm.com>
Signed-off-by: Sivan Reinstein <sivanr@codeaurora.org>