Staging: gdm724x: Use ALIGN() macro for dummy_cnt in gdm_mux.c

As suggested in TODO list, this patch uses ALIGN() macro for variable
dummy_cnt in functions up_to_host() and gdm_mux_send() in file
gdm_mux.c.
The macro has already been defined in include/linux/kernel.h, hence is
not defined again.

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>