global: Make ARCH_MISC_INIT a selected symbol

global: Make ARCH_MISC_INIT a selected symbol

This symbol is not something that the user should be enabling or
disabling but rather the developer for a particular board should select
it when required.

This is mostly size neutral, however a few places do have changes. In
the case of i.MX6ULL systems, it is always the case that
arch_misc_init() could call setup_serial_number() and do useful work,
but was not enabled widely, but now is. In the case of i.MX23/28
systems, we should be able to call mx28_fixup_vt() again here, so do so.
Finally, some platforms were calling arch_misc_init() and then not doing
anything and this results in removing the option.

Acked-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>