msm: mdss: enable mmagic gdsc before calling SMMUv2 APIs

SMMUv2 clients needs to enable the mmagic gdsc before
creating mapping or attaching context bank. It can disable
the GDSC when context banks are detached. Display module
enables mmagic gdsc before creating secure & unsecure
context bank mapping for MDP and rotation clients during
probe. This GDSC is also turned on and off when clients
tries to attach context banks and detach respectively.

Change-Id: Iee3c93d440388693d83cc57ca001408d95c9654b
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>