ARM: mxc: don't use the symbols in the CPU family choice to select others

The symbols in this choice should only be used to select between the
available machines that can be built into a single kernel. As these sets
(will) differ e.g. depending on ARM_PATCH_PHYS_VIRT and AUTO_ZRELADDR
letting them select other symbols makes the logic more complex and needs
to duplicate some things. So let the machines select the corresponding
symbols (indirectly via SOC_XYZ).

LAKML-Reference: 1302464943-20721-2-git-send-email-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>