Staging: comedi:Fix a warning issues in me_daq.c

This is a patch to the me_daq.c file that fixes up a
WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
found by the checkpatch.pl tool.

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>