ARM: link board specific files after core files

This allows for board specific issues to override decisions made in generic
code that might not be suitable due to some errata or the like, by making
the initcall hooks from those board specific files run after the core ones,
therefore avoiding ugly #ifdef's in core code.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Tested-by: Dave Martin <dave.martin@linaro.org>
Tested-by: Jason Hui <jason.hui@linaro.org>