m68k: Remove M5475x boards

These board has not been converted to CONFIG_DM_PCI by the deadline.
Remove them.  As this is the last of the mcf547x_8x family of boards,
remove that support as well.

Cc: TsiChung Liew <Tsi-Chung.Liew@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>