radeon: use max_bus_speed to activate gen2 speeds

radeon currently uses a drm function to get the speed capabilities for
the bus, drm_pcie_get_speed_cap_mask. However, this is a non-standard
method of performing this detection and this patch changes it to use
the max_bus_speed attribute.

From: Lucas Kannebley Tavares <lucaskt@linux.vnet.ibm.com>
Signed-off-by: Kleber Sacilotto de Souza <klebers@linux.vnet.ibm.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
index 8f9e2d3..8546e3b 100644
--- a/drivers/gpu/drm/radeon/evergreen.c
+++ b/drivers/gpu/drm/radeon/evergreen.c
@@ -4999,8 +4999,7 @@
 
 void evergreen_pcie_gen2_enable(struct radeon_device *rdev)
 {
-	u32 link_width_cntl, speed_cntl, mask;
-	int ret;
+	u32 link_width_cntl, speed_cntl;
 
 	if (radeon_pcie_gen2 == 0)
 		return;
@@ -5015,11 +5014,8 @@
 	if (ASIC_IS_X2(rdev))
 		return;
 
-	ret = drm_pcie_get_speed_cap_mask(rdev->ddev, &mask);
-	if (ret != 0)
-		return;
-
-	if (!(mask & DRM_PCIE_SPEED_50))
+	if ((rdev->pdev->bus->max_bus_speed != PCIE_SPEED_5_0GT) &&
+		(rdev->pdev->bus->max_bus_speed != PCIE_SPEED_8_0GT))
 		return;
 
 	speed_cntl = RREG32_PCIE_PORT(PCIE_LC_SPEED_CNTL);