[arch][m68k] initial port to m68k

Uses the QEMU virt machine for 68k defined in qemu 6.0+.
Basic support that boots, prints to the console, takes input from
console, and context switches.

TODO: interrupt support, timer support.

target/qemu-virt-m68k/rules.mk

@@ -0,0 +1,5 @@
+LOCAL_DIR := $(GET_LOCAL_DIR)
+
+MODULE := $(LOCAL_DIR)
+
+PLATFORM := qemu-virt-m68k