ARM: OMAP4: Remove __INIT from omap_secondary_startup() to re-use it for hotplug.

Remove the __INIT from omap_secondary_startup() so that it can
be re-used for CPU hotplug.

While at this, remove the un-used AUXBOOT register reference.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Jean Pihet <j-pihet@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Vishwanath BS <vishwanath.bs@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>