sparc,leon: support for GRPCI1 PCI host bridge controller

Some of the GRPCI1 cores does not support detection of all PCI
errors, the default is therefore limited PCI error handling.
The property all_pci_errors my be set by the boot loader to
enable interrupt on all PCI errors.

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>