staging: dgap: Merge dgap_tty.h into dgap_driver.c

There is a lot of cleanup work to do on these digi drivers and merging as
much as is possible will make it easier. I also notice that many merged
drivers are single source and header.

Signed-off-by: Mark Hounschell <markh@compro.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --cc drivers/staging/dgap/dgap_driver.c
Simple merge

diff --cc drivers/staging/dgap/dgap_tty.h
Simple merge