Revert "tty/serial: atmel: fix out of range clock divider handling"

This reverts commit 751d0017.

The wrong commit got added to the tty-next tree, the correct one is in
the tty-linus branch.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: David Engraf <david.engraf@sysgo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>