MIPS: Remove no longer needed work_on_cpu() call

MIPS: Remove no longer needed work_on_cpu() call

Since commit 354a9025185a ("cpu/hotplug: Fix rollback during error-out
in __cpu_disable()") it is ensured that callbacks of CPU_ONLINE and
CPU_DOWN_PREPARE are processed on the hotplugged CPU. Due to this
work_on_cpu() calls are no longer required.

Replace work_on_cpu() with a direct call of mips_cdmm_bus_up() or
mips_cdmm_bus_down(). Description of those functions are adapted.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: rt@linutronix.de
Patchwork: https://patchwork.linux-mips.org/patch/13197/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>