staging: comedi: Use the BIT() macro instead of left shifting 1

This patch replaces left shifts on 1 with the BIT(x) macro, as suggested
by checkpatch.pl.

Signed-off-by: sayli karnik <karniksayli1995@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>