tty: n_gsm, remove duplicates of parameters

commit b93db97e

 upstream.

dp, f, and i are only duplicates of gsmld_receive_buf's parameters. Use
the parameters directly (cp, fp, and count) and delete these local
variables.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210302062214.29627-41-jslaby@suse.cz
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@infotecs.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>