msm: ipa3: fix the unmap logic

Ethenet driver npn phy address was same for UL/DL
pipes, currently this address was unmapped during
DL pipe disconnect where UL pipe still avtive,
move the logic to do the unmamp to the last pipe
disconnect.

Change-Id: I697edb844b8134d2a1d52e3c2bcfd0a7066edb2f
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>