staging: comedi: amplc_pc263: Add attach_pci() hook

Implement the attach_pci() hook as function pc263_attach_pci().  This is
called bu comedi_pci_auto_config() in preference to the old attach()
hook (implemented by pc263_attach()) and avoids searching for the probed
PCI device.

Factor out code common to pc263_find_pci() and pc263_attach_pci() into
new function pc263_find_pci_board().  Factor out most code common to
pc263_attach() and pc263_attach_pci() into new functions
pc263_pci_common_attach() and pc263_common_attach().

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>