User UART3 on HiKey board.

This is more commonly used for firmware and kernel logs and, more
importantly, is easier to access thanks to the mezzanine board.

Change-Id: I076aefc3f66b8de85081a3fd1cf69acef671b6f0
diff --git a/build/arch/aarch64/hikey.args b/build/arch/aarch64/hikey.args
index dfdf0d6..d08989d 100644
--- a/build/arch/aarch64/hikey.args
+++ b/build/arch/aarch64/hikey.args
@@ -1,5 +1,6 @@
 arch_cpu = "cortex-a57+nofp"
 arch_hypervisor_origin_address = "0x01000000"
 
+# Use UART3.
 arch_aarch64_use_pl011 = true
-arch_aarch64_pl011_base_address = "0xf8015000"
+arch_aarch64_pl011_base_address = "0xf7113000"