video: fbdev: w100fb: fix sparse warnings

* Add missing __iomem annotations where needed.
* Make w100fb_probe() static.
* Return NULL pointer (instead of using plain integer) in
  w100_get_xtal_tabl().
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/d438108a-e569-a14a-a9b1-3fefd88fcadc@samsung.com

drivers/video/fbdev/w100fb.c

@@ -61,9 +61,9 @@ struct w100_pll_info *w100_get_xtal_table(unsigned int freq);
 #define BITS_PER_PIXEL    16
 
 /* Remapped addresses for base cfg, memmapped regs and the frame buffer itself */
-static void *remapped_base;
-static void *remapped_regs;
-static void *remapped_fbuf;
+static void __iomem *remapped_base;
+static void __iomem *remapped_regs;
+static void __iomem *remapped_fbuf;
 
 #define REMAPPED_FB_LEN   0x15ffff
 
@@ -635,7 +635,7 @@ static int w100fb_resume(struct platform_device *dev)
 #endif
 
 
-int w100fb_probe(struct platform_device *pdev)
+static int w100fb_probe(struct platform_device *pdev)
 {
 	int err = -EIO;
 	struct w100fb_mach_info *inf;
@@ -807,10 +807,11 @@ static int w100fb_remove(struct platform_device *pdev)
 
 static void w100_soft_reset(void)
 {
-	u16 val = readw((u16 *) remapped_base + cfgSTATUS);
-	writew(val | 0x08, (u16 *) remapped_base + cfgSTATUS);
+	u16 val = readw((u16 __iomem *)remapped_base + cfgSTATUS);
+
+	writew(val | 0x08, (u16 __iomem *)remapped_base + cfgSTATUS);
 	udelay(100);
-	writew(0x00, (u16 *) remapped_base + cfgSTATUS);
+	writew(0x00, (u16 __iomem *)remapped_base + cfgSTATUS);
 	udelay(100);
 }
 
@@ -1022,7 +1023,8 @@ struct w100_pll_info *w100_get_xtal_table(unsigned int freq)
 			return pll_entry->pll_table;
 		pll_entry++;
 	} while (pll_entry->xtal_freq);
-	return 0;
+
+	return NULL;
 }