m68k: add board stmark2, mcf5441x based

Sysam stmark2 board is a generic and fully (hw and sw) open board, with
a mcf54415 Coldfire CPU, 128MB of DDR2, 16MB of SPI flash and SD card
as non volatile memories, and a wifi module included on-board.
The board is actually used mainly for Coldfire custodian testing activity
related to the mcf5441x Coldfire family.

For further information please see: http://sysam.it/cff_stmark2.html



Signed-off-by: Angelo Dureghello <angelo@sysam.it>
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Changes in v2:
 - remove CMD_REGINFO
 - add board information in commit message