MIPS: asm: pci: define arch-specific 'pci_remap_iospace()' dependent on 'CONFIG_PCI_D...

MIPS: asm: pci: define arch-specific 'pci_remap_iospace()' dependent on 'CONFIG_PCI_DRIVERS_GENERIC'

Some MIPS defconfigs that don't define 'CONFIG_PCI_DRIVERS_GENERIC' but
define 'CONFIG_PCI_DRIVERS_LEGACY' or none of them, can fail when they are
built since definition for 'pci_remap_iospace' is being done in include
file 'arch/mips/include/asm/pci.h' and the specific function implemented
in 'arch/mips/pci/pci-generic.c'. MIPS PCI drivers that don't use generic
PCI core APIs don't really need 'pci_remap_iospace' to be defined at all.
Hence, change definition for 'pci_remap_iospace' to be dependent on the
preprocessor 'CONFIG_PCI_DRIVERS_GENERIC' definition to avoid possible
build problems.

Fixes: 9f76779f2418 ("MIPS: implement architecture-specific 'pci_remap_iospace()'")
CC: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20211008095311.26475-1-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>