ARM: SoC: convert OMAP4 to SMP operations

Convert OMAP4 to use struct smp_operations to provide its SMP
and CPU hotplug operations.

Tested on both Panda and IGEPv2 (MULTI_OMAP kernel)

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>