drm/amdgpu: Fix num_doorbell calculation issue

When paging queue is enabled, it use the second page of doorbell.
The AMDGPU_DOORBELL64_MAX_ASSIGNMENT definition assumes all the
kernel doorbells are in the first page. So with paging queue enabled,
the total kernel doorbell range should be original num_doorbell plus
one page (0x400 in dword), not *2.
Signed-off-by: NOak Zeng <ozeng@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -539,10 +539,13 @@ static int amdgpu_device_doorbell_init(struct amdgpu_device *adev)
 		return -EINVAL;
 
 	/* For Vega, reserve and map two pages on doorbell BAR since SDMA
-	 * paging queue doorbell use the second page
+	 * paging queue doorbell use the second page. The
+	 * AMDGPU_DOORBELL64_MAX_ASSIGNMENT definition assumes all the
+	 * doorbells are in the first page. So with paging queue enabled,
+	 * the max num_doorbells should + 1 page (0x400 in dword)
 	 */
 	if (adev->asic_type >= CHIP_VEGA10)
-		adev->doorbell.num_doorbells *= 2;
+		adev->doorbell.num_doorbells += 0x400;
 
 	adev->doorbell.ptr = ioremap(adev->doorbell.base,
 				     adev->doorbell.num_doorbells *