MIPS: Don't overflow cevt-r4k.c calculations at high clock rates.

The 'mult' element of struct clock_event_device must never be wider
than 32-bits.  If it were, it would get truncated when used by
clockevent_delta2ns() when this calls do_div().

We can meet this requirement by using clockevent_set_clock() to set
the MULT and SHIFT values.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1253/


Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>