ARM: msm: Simplify ARCH_MSM_DT config

This doesn't need to be a def_bool y. Instead we can have every
DT supported platform select ARCH_MSM_DT and we achieve the same
thing with less chance of conflicts.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>
Signed-off-by: Olof Johansson <olof@lixom.net>