zoran: don't bother with struct file * in zoran_map

zoran: don't bother with struct file * in zoran_map

all we need it for is file->private_data, which is assign-once, already
assigned by that point and, incidentally, its value is already in use
by zoran ->mmap() anyway.  So just store that pointer instead...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>