Staging: comedi: dmm32at: fix BIT macro issue.

This Replace all occurences of (1<<x) by BIT(x) and DMM32AT_CTRL_PAGE(x),
DMM32AT_AI_CFG_SCINT(x) macros to get rid of checkpatch.pl
"CHECK" output "Prefer using the BIT macro"

Signed-off-by: Ravishankar Karkala Mallikarjunayya <ravishankarkm32@gmail.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>