fs/char_dev.c: remove pointless assignment from __register_chrdev_region()

At one place we assign major number we found to ret.  That assignment is
then never used and actually doesn't make any sense given how the code is
currently structured (the assignment comes from pre-git times).  Just
remove it.

Coverity id: 1226852.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>