msm: kgsl: Trigger GBIF GX halt only if GX is ON

Trigger GBIF GX halt only if GX HS is ON because GBIF
GX halt is not required if GX HS is in collapsed state.

Change-Id: If60192546d61a83a6e023f7c0323ce953f6ef3e7
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>