clocksource/drivers/mips-gic-timer: Refine rating computation

clocksource/drivers/mips-gic-timer: Refine rating computation

It is a good clocksource which usually go as fast as CPU core
and have a low access latency, so raise the base of rating
from Good to desired when we know that it has a stable frequency.

Increase frequency addend dividend to 10000000 (10MHz) to
reasonably accommodate multi GHz level clock, also cap rating
within current level.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Link: https://lore.kernel.org/r/20240612-mips-clks-v2-6-a57e6f49f3db@flygoat.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>