msm: ipa: fix to IPA endpoints allocation

According to the architecture document, endpoint 10 should be in the
control of Q6, therefore, allocate endpoint 10 to Q6_DUN_CONS client and
endpoint 15 to USB_CONS client.

Also added a new client, IPA_CLIENT_Q6_DUN_CONS so that endpoint 10 will
not be mistakenly allocated to another client in the future.

Change-Id: I4153585a479abeb3eeffc05cdf43ccdd5a5eed9e
Signed-off-by: Gidon Studinski <gidons@codeaurora.org>