bcma: handle return value of pci_assign_resource

This fixes the following warning:

  CC      drivers/bcma/driver_pci_host.o
drivers/bcma/driver_pci_host.c: In function 'bcma_core_pci_fixup_addresses':
drivers/bcma/driver_pci_host.c:555:23: error: ignoring return value of
'pci_assign_resource', declared with attribute warn_unused_result
[-Werror=unused-result]

Reported-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>