CBMEM: Always use DYNAMIC_CBMEM

Drop the implementation of statically allocated high memory
region for CBMEM. There is no longer the need to explicitly
select DYNAMIC_CBMEM, it is the only remaining choice.

Change-Id: Iadf6f27a134e05daa1038646d0b4e0b8f9f0587a
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/7851
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/cpu/ti/am335x/Kconfig

@@ -7,7 +7,6 @@ config CPU_TI_AM335X
 	select HAVE_UART_SPECIAL
 	select BOOTBLOCK_CONSOLE
 	select CPU_HAS_BOOTBLOCK_INIT
-	select DYNAMIC_CBMEM
 	bool
 	default n