staging/xgifb: mttr must be (signed) int

The mttr field must be declared as signed int (as in every other fb
driver) for the mttr functions to work properly.
Moreover the value should be initialized with -1.
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/xgifb/XGI_main_26.c

@@ -1802,7 +1802,7 @@ static int xgifb_probe(struct pci_dev *pdev,
 	if (!XGIInitNew(pdev))
 		dev_err(&pdev->dev, "XGIInitNew() failed!\n");
 
-	xgifb_info->mtrr = (unsigned int) 0;
+	xgifb_info->mtrr = -1;
 
 	xgifb_info->hasVB = HASVB_NONE;
 	if ((xgifb_info->chip == XG20) ||

drivers/staging/xgifb/XGIfb.h

@@ -67,7 +67,7 @@ struct xgifb_video_info {
 	unsigned long mmio_size;
 	void __iomem *mmio_vbase;
 	unsigned long vga_base;
-	unsigned long mtrr;
+	int mtrr;
 
 	int    video_bpp;
 	int    video_cmap_len;