of: remove unused pci_space variable from address.c

It was never used and could be removed, otherwise
we could see a warning:

drivers/of/address.c: In function 'of_pci_range_parser_one':
drivers/of/address.c:277:14: warning: variable 'pci_space' set but not
used [-Wunused-but-set-variable]

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Rob Herring <robh@kernel.org>