of: fix sparse warning in of_pci_range_parser_one

sparse gives the following warning for 'pci_space':

../drivers/of/address.c:266:26: warning: incorrect type in assignment (different base types)
../drivers/of/address.c:266:26:    expected unsigned int [unsigned] [usertype] pci_space
../drivers/of/address.c:266:26:    got restricted __be32 const [usertype] <noident>

It appears that pci_space is only ever accessed on powerpc, so the endian
swap is often not needed.

Cc: stable@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>