staging: comedi: daqboard2000: remove local variable in daqboard2000_attach_pci()

The 'pci_base' variable is only used to hold the pci_resource_start()
value used to ioremap the pci bars. Remove the local variable and just
use pci_resource_start() directly in the ioremap.

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>