Fix a few incorrectly checked [io_]remap_pfn_range() calls

Nico Golde reports a few straggling uses of [io_]remap_pfn_range() that
really should use the vm_iomap_memory() helper.  This trivially converts
two of them to the helper, and comments about why the third one really
needs to continue to use remap_pfn_range(), and adds the missing size
check.

Reported-by: Nico Golde <nico@ngolde.de>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org.
diff --git a/drivers/video/au1100fb.c b/drivers/video/au1100fb.c
index a54ccdc..22ad8524 100644
--- a/drivers/video/au1100fb.c
+++ b/drivers/video/au1100fb.c
@@ -361,37 +361,13 @@
 int au1100fb_fb_mmap(struct fb_info *fbi, struct vm_area_struct *vma)
 {
 	struct au1100fb_device *fbdev;
-	unsigned int len;
-	unsigned long start=0, off;
 
 	fbdev = to_au1100fb_device(fbi);
 
-	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT)) {
-		return -EINVAL;
-	}
-
-	start = fbdev->fb_phys & PAGE_MASK;
-	len = PAGE_ALIGN((start & ~PAGE_MASK) + fbdev->fb_len);
-
-	off = vma->vm_pgoff << PAGE_SHIFT;
-
-	if ((vma->vm_end - vma->vm_start + off) > len) {
-		return -EINVAL;
-	}
-
-	off += start;
-	vma->vm_pgoff = off >> PAGE_SHIFT;
-
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 	pgprot_val(vma->vm_page_prot) |= (6 << 9); //CCA=6
 
-	if (io_remap_pfn_range(vma, vma->vm_start, off >> PAGE_SHIFT,
-				vma->vm_end - vma->vm_start,
-				vma->vm_page_prot)) {
-		return -EAGAIN;
-	}
-
-	return 0;
+	return vm_iomap_memory(vma, fbdev->fb_phys, fbdev->fb_len);
 }
 
 static struct fb_ops au1100fb_ops =