Make the code simpler and open the way for device tree clocks.

[ralf@linux-mips.org: Resolved conflict with 2a552da6 (MIPS/IRQCHIP: Move
irq_chip from arch/mips to drivers/irqchip.)]
Signed-off-by: Alban Bedel <albeu@free.fr>
Cc: linux-mips@linux-mips.org
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Qais Yousef <qais.yousef@imgtec.com>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Cc: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9774/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>