Probe for GICv3 re-distributors on core bring-up

The GICv3 distributor can have more ports than CPUs are available in
the system. Probe all re-distributors and use the matching affinity
levels as specified by each core and re-distributor to decide which
re-distributor to use with which CPU core.

If a core cannot be matched with a re-distributor, the core panics and
is placed in an endless loop.

Change-Id: Ie393cfe07c7449a2383959e3c968664882e18afc
diff --git a/include/mmio.h b/include/mmio.h
index b72daca..313448e 100644
--- a/include/mmio.h
+++ b/include/mmio.h
@@ -38,6 +38,9 @@
 extern void mmio_write_32(uintptr_t addr, uint32_t value);
 extern uint32_t mmio_read_32(uintptr_t addr);
 
+extern void mmio_write_64(uintptr_t addr, uint64_t value);
+extern uint64_t mmio_read_64(uintptr_t addr);
+
 #endif /*__ASSEMBLY__*/
 
 #endif /* __MMIO_H__ */