drm/hisilicon: Fix build error

Fix the following errors:
divers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c:
In function ‘hibmc_hw_map’:
drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c:213:25:
error: ‘dev’ undeclared (first use in this function);

Fixes: 4d4dad21cc ("drm/hibmc: Remove references to struct drm_device.pdev")
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1610529568-25754-1-git-send-email-tiantao6@hisilicon.com

drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c

@@ -210,7 +210,7 @@ static void hibmc_hw_config(struct hibmc_drm_private *priv)
 
 static int hibmc_hw_map(struct hibmc_drm_private *priv)
 {
-	struct pci_dev *pdev = dev->pdev;
+	struct drm_device *dev = &priv->dev;
 	struct pci_dev *pdev = to_pci_dev(dev->dev);
 	resource_size_t addr, size, ioaddr, iosize;