ARM: OMAP2+: Limit omap initcalls to omap only on multiplatform kernels

We need to make sure that multiplatform kernels don't
run omap initcalls when booted on other SoCs.

Do this by adding wrapper macros for the initcalls that
return early if soc_is_omap() test fails. This allows
us to easily change the defines later if we have SoC
specific init sections available.

Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>