ep93xx: Move peripheral defines to local SoC header

Move the AHB/APB peripheral defines to local SoC header since they are
only needed by the core SoC code. The UART defines are not moved
because they are used by the mach/uncompress.h header.

Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Reviewed-by: Mika Westerberg <mika.westerberg@iki.fi>
Acked-by: Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>