[platform][rosco-m68k] Add port to the Rosco M68k board

Port to the really neat 68010 based board at https://rosco-m68k.com/

Port Features:
-10Mhz 68010
-1MB ram
-Dual UART + timer implemented as a 68c681 chip
-timer running at 1Khz, UART A for console
-interrupt driven RX support

Some amount of extending of the 68k exceptinon code was needed to
support the autovectored irqs that the 68681 uart uses. Added build
system support for 68010.

target/rosco-m68k/rules.mk

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