ARM: davinci: multi-soc kernels require AUTO_ZRELADDR

The davinci DA8xx and DMx families have incompatible zreladdr
settings, and attempting to build a kernel with both enabled
results in an error unless AUTO_ZRELADDR is set:

multiple zreladdrs: 0xc0008000 0x80008000
This needs CONFIG_AUTO_ZRELADDR to be set

This patch changes Kconfig to make the two families mutually
exclusive when this is unset.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>