of/irq: provide more wrappers for !CONFIG_OF

The pci-rcar driver is enabled for compile tests, and this has
now shown that the driver cannot build without CONFIG_OF,
following the inclusion of f8f2fe73

 "PCI: rcar: Use new OF
interrupt mapping when possible":

drivers/built-in.o: In function `rcar_pci_map_irq':
:(.text+0x1cc7c): undefined reference to `of_irq_parse_and_map_pci'
pci/host/pcie-rcar.c: In function 'pci_dma_range_parser_init':
pci/host/pcie-rcar.c:875:2: error: implicit declaration of function 'of_n_addr_cells' [-Werror=implicit-function-declaration]

As pointed out by Ben Dooks and Geert Uytterhoeven, this is actually
supposed to build fine, which we can achieve if we make the
declaration of of_irq_parse_and_map_pci conditional on CONFIG_OF
and provide an empty inline function otherwise, as we do for
a lot of other of interfaces.

This lets us build the rcar_pci driver again without CONFIG_OF
for build testing. All platforms using this driver select OF,
so this doesn't change anything for the users.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: devicetree@vger.kernel.org
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Magnus Damm <damm@opensource.se>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: linux-pci@vger.kernel.org
Cc: linux-sh@vger.kernel.org
[robh: drop wrappers for of_n_addr_cells and of_n_size_cells which are
low-level functions that should not be used for !OF]
Signed-off-by: Rob Herring <robh@kernel.org>