staging: comedi: mite.h: rename CHSR_LxERR_mask

Fix the checkpatch.pl issue:
CHECK: Avoid CamelCase: <CHSR_LxERR_mask>

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>