[PATCH] fbdev: Sanitize ->fb_mmap prototype

No need for a file argument.  If we'd really need it it's in vma->vm_file
already.  gbefb and sgivwfb used to set vma->vm_file to the file argument, but
the kernel alrady did that.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>