staging: comedi: remove the comed_alloc_subdevices "allocation failed" messages

Remove all the "allocation failed" debug messages that are displayed
when the comedi_alloc_subdevices call fails.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbot <abbott@mev.co.uk>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>