Revert "ARM: arch_timer: use full 64-bit counter for sched_clock"

This reverts commit 023796b9.
Leaving the timer running in the bootloader and booting the
kernel later causes the sched_clock values to return very large
values. This also fails to stop sched_clock during suspend
leading to problems with RT threads.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>