ARM: OMAP: Warn if omap_ioremap is called before SoC detection

We don't have cpu_is_omapxxxx SoC detection initialized until
SoC detection is initialized from init_early.

Note that with the common map_io we should no longer need
cpu_is_omapxxxx for ioremap.

Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>