powerpc/isa-bridge: Remove open coded "ranges" parsing

"ranges" is a standard property with common parsing functions. Users
shouldn't be implementing their own parsing of it. Reimplement the
ISA brige "ranges" parsing using the common ranges iterator functions.

The common routines are flexible enough to work on PCI and non-PCI to
ISA bridges, so refactor pci_process_ISA_OF_ranges() and
isa_bridge_init_non_pci() into a single implementation.

Signed-off-by: Rob Herring <robh@kernel.org>
[mpe: Unsplit some strings and use pr_xxx()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230327223045.819852-1-robh@kernel.org