drm/msm/iommu: rename msm_fault_handler to msm_gpu_fault_handler

In preparation of registering a separate fault handler for
display, lets rename the existing msm_fault_handler to
msm_gpu_fault_handler.

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/638358/
Link: https://lore.kernel.org/r/20250219-abhinavk-smmu-fault-handler-v3-2-aa3f0bf4434a@quicinc.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>