radeon: use pdev->pm_cap instead of pci_find_capability(..,PCI_CAP_ID_PM)

Pci core has been saved pm cap register offset by pdev->pm_cap in pci_pm_init()
in init path. So we can use pdev->pm_cap instead of using
pci_find_capability(pdev, PCI_CAP_ID_PM) for better performance and simplified code.
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-fbdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/aty/radeon_pm.c

@@ -2805,7 +2805,7 @@ static void radeonfb_early_resume(void *data)
 void radeonfb_pm_init(struct radeonfb_info *rinfo, int dynclk, int ignore_devlist, int force_sleep)
 {
 	/* Find PM registers in config space if any*/
-	rinfo->pm_reg = pci_find_capability(rinfo->pdev, PCI_CAP_ID_PM);
+	rinfo->pm_reg = rinfo->pdev->pm_cap;
 
 	/* Enable/Disable dynamic clocks: TODO add sysfs access */
 	if (rinfo->family == CHIP_FAMILY_RS480)