alpha: Allow HZ to be configured

With the 1024Hz default, we spend 50% of QEMU emulation
processing timer interrupts.

Signed-off-by: Richard Henderson <rth@twiddle.net>

diff --cc arch/alpha/Kconfig
Simple merge

diff --cc arch/alpha/kernel/setup.c
Simple merge

diff --cc arch/alpha/kernel/time.c
Simple merge