msm: cpp: Change CPP IOMMU contex name according dtsi

MSM8994 IOMMU dtsi defines the contex which cpp have to
use. CPP driver have to use the same contex name as the
one specified in the dtsi.

Change-Id: Ida87210dcd4ee39494f6ab6a61290aec8de1afe9
Signed-off-by: Iliya Varadzhakov <ivarad@codeaurora.org>