at91: defined mach-types for otc570 board in board config file

quotation from Albert ARIBAUD:
"Recently the ARM mach-types.h file has been brought in sync with its
Linux original, leasing to a number of boards not being listed any more,
as the new list only contains boards which have actual Linux support or
were declared less than one year ago.

The symptom is a build failure with a message of the form "error:
'MACH_TYPE_XXXXXX' undeclared (first use in this function)".

U-Boot maintainers of such boards (in Cc: of this mail) should provide a
patch to re-introduce the MACH_TYPE_XXXXXX definition in their boards'
config header file in include/configs/."

Signed-off-by: Daniel Gorsulowski <Daniel.Gorsulowski@esd.eu>