ARM: bcm281xx: symbol cleanup

This patch renames a few symbols that needlessly used "11351" rather
than "281xx" in their names.

Support for the bcm11351 board is being removed from the kernel, and
the family of boards is more properly referred to as "bcm281xx".

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
Signed-off-by: Matt Porter <mporter@linaro.org>