hz,efikamx: use kernel/Kconfig.hz like every other arch and respect selection

I have no idea why there is a "default 100" in the arch/arm/Kconfig list
but it is resetting all attempts to select a faster timer frequency. Now
that we have CONFIG_NO_HZ a timer frequency of "1000" is of only minimal
power increase over a static HZ of 100, since the timer will not fire that
often anyway - but HZ does inform other aspects of the kernel and improves
timer latency (in effect, HZ defines how many timer events CAN happen in
one second in the sense that CONFIG_NO_HZ will batch timer events. If no
timer events happen, nothing happens, but if a lot happen, you want them
serviced in smaller batches to reduce latency).

Sometimes 100 may not be enough for multimedia (as per kernel/Kconfig.hz)
and we love to do multimedia here, so update our defconfig along with the
patch. Just because your ARM platform has no high resolution timers worth
a damn doesn't mean we all have to suffer or add ridiculous platform-specific
defaults.