drm/amdgpu: Remove writing GRBM_GFX_CNTL in RLCG interface under SRIOV

[Why]
Accessing GRBM_GFX_CNTL in full access time has risk when VF is doing MMIO attacking.
Therefore, VF writing GRBM_GFX_CNTL are blocked by L1 Policy.
For RLCG interface, RLCG use SCRATCH_REG2 which is copied from GRBM_GFX_CNTL.

[How]
Remove writing GRBM_GFX_CNTL in amdgpu_virt_rlcg_reg_rw.

v2:
Remove directly writing GRBM_GFX_INDEX in amdgpu_virt_rlcg_reg_rw
as RLCG interface no need to use it.
Signed-off-by: Yifan Zha <Yifan.Zha@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c

@@ -983,11 +983,9 @@ static u32 amdgpu_virt_rlcg_reg_rw(struct amdgpu_device *adev, u32 offset, u32 v
 	if (offset == reg_access_ctrl->grbm_cntl) {
 		/* if the target reg offset is grbm_cntl, write to scratch_reg2 */
 		writel(v, scratch_reg2);
-		writel(v, ((void __iomem *)adev->rmmio) + (offset * 4));
 	} else if (offset == reg_access_ctrl->grbm_idx) {
 		/* if the target reg offset is grbm_idx, write to scratch_reg3 */
 		writel(v, scratch_reg3);
-		writel(v, ((void __iomem *)adev->rmmio) + (offset * 4));
 	} else {
 		/*
 		 * SCRATCH_REG0 	= read/write value