staging: dgap: Merge dgap_tty.c 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>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgap/Makefile

@@ -3,5 +3,5 @@ obj-$(CONFIG_DGAP) += dgap.o
 
 dgap-objs :=	dgap_driver.o   dgap_fep5.o \
 		dgap_parse.o	dgap_trace.o \
-		dgap_tty.o	dgap_sysfs.o
+		dgap_sysfs.o