drm/radeon: use pcie_get_readrq() and pcie_set_readrq() to simplify code

Use pcie_get_readrq() and pcie_set_readrq() functions to simplify code.
Signed-off-by: NYijing Wang <wangyijing@huawei.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/evergreen.c

@@ -1174,23 +1174,16 @@ int evergreen_set_uvd_clocks(struct radeon_device *rdev, u32 vclk, u32 dclk)
 
 void evergreen_fix_pci_max_read_req_size(struct radeon_device *rdev)
 {
-	u16 ctl, v;
-	int err;
-
-	err = pcie_capability_read_word(rdev->pdev, PCI_EXP_DEVCTL, &ctl);
-	if (err)
-		return;
-
-	v = (ctl & PCI_EXP_DEVCTL_READRQ) >> 12;
+	int readrq;
+	u16 v;
 
+	readrq = pcie_get_readrq(rdev->pdev);
+	v = ffs(readrq) - 8;
 	/* if bios or OS sets MAX_READ_REQUEST_SIZE to an invalid value, fix it
 	 * to avoid hangs or perfomance issues
 	 */
-	if ((v == 0) || (v == 6) || (v == 7)) {
-		ctl &= ~PCI_EXP_DEVCTL_READRQ;
-		ctl |= (2 << 12);
-		pcie_capability_write_word(rdev->pdev, PCI_EXP_DEVCTL, ctl);
-	}
+	if ((v == 0) || (v == 6) || (v == 7))
+		pcie_set_readrq(rdev->pdev, 512);
 }
 
 static bool dce4_is_in_vblank(struct radeon_device *rdev, int crtc)