mpc8xxx: fix DDR init value to use CONFIG_MEM_INIT_VALUE

Configuring custom memory init value using CONFIG_MEM_INIT_VALUE in
the board config file doesn't work and memory is always initialized
to the value 0xdeadbeef. Only use this default value if a board doesn't
define CONFIG_MEM_INIT_VALUE.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Andy Fleming <afleming@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
1 file changed