MIPS: PowerTV: Remove extra r4k_clockevent_init() call

A call to r4k_clocksource_init() was added to plat_time_init(), but
when init_mips_clock_source() calls the same function, boot fails in
clockevents_register_device(). This patch removes the extraneous call.

Signed-off-by: David VomLehn <dvomlehn@cisco.com>
Patchwork: http://patchwork.linux-mips.org/patch/803/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>