staging: comedi: addi-data: add a 'pcidev' local var to i_ADDI_Attach()

Add a local variable for the pci_dev pointer to make the code a
bit cleaner.

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>