ARM: armv7: add non-SPL enable for Cortex SMPEN

Commit 2564fce7 ("sunxi: move Cortex SMPEN setting into start.S")
added SPL_ARMV7_SET_CORTEX_SMPEN to enable setting SMP bit. For
platforms not using SPL boot, add the corresponding non-SPL config,
so that CONFIG_IS_ENABLED(ARMV7_SET_CORTEX_SMPEN) works as expected.

Signed-off-by: Ralph Siemsen <ralph.siemsen@linaro.org>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>