arc: use timer driver for ARC boards

This commit replaces legacy timer code with usage of arc timer
driver.

It removes arch/arc/lib/time.c file and selects CONFIG_CLK,
CONFIG_TIMER and CONFIG_ARC_TIMER options for all ARC boards by default.
Therefore we remove CONFIG_CLK option from less common axs101 and
axs103 defconfigs.

Also it removes legacy CONFIG_SYS_TIMER_RATE config symbol from
axs10x.h, tb100.h and nsim.h configs files as it is no longer required.

Signed-off-by: Vlad Zakharov <vzakhar@synopsys.com>
Reviewed-by: Simon Glass <sjg@chromium.org>