staging: dgap: tty.c: removes read_cnt, real_raw and rawreadok

This patch removes the use of read_cnt, real_raw and rawreadok.
These variables don't exist in the new API. Reading the data
raw is no longer supported by the tty layer.

Signed-off-by: Lidza Louina <lidza.louina@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>