ARM: realview: activate SMP on the default defconfig

The realview has two defconfigs: realview_defconfig and
realview-smp_defconfig. We now have working SMP_ON_UP so
make them equal so we can delete the -smp variant. For
some reason NO_HZ_FULL was missing from the plain
realview_defconfig.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>