staging: comedi: s526: rename local var used for CR_CHAN() value

Rename the local variable used to hold the unpacked CR_CHAN() value
to help keep the lines < 80 chars.

Also, since the insn->chanspec variable is an unsigned int, change
the type of the local variable to match.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>