clocksource: mips-gic-timer: Use new GIC accessor functions

Switch from calling functions exported by the GIC interrupt controller
to using new accessors provided by asm/mips-gic.h. This will allow the
counter-handling functionality to be removed from the interrupt
controller driver, where it doesn't really belong, and also allow for
inlining of the accesses to the GIC.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17021/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>