MIPS: csrc-r4k: Refine rating computation

Increase frequency addend dividend to 10000000 (10MHz) to
reasonably accommodate multi GHz level mips_hpt_frequency.

Cap rating of csrc-r4k into 299 to ensure it doesn't go into
"Desired" range, given all the drama we have with CP0 count
registers (SMP sync, behaviour on wait etc).
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/kernel/csrc-r4k.c

@@ -111,7 +111,8 @@ int __init init_r4k_clocksource(void)
 		return -ENXIO;
 
 	/* Calculate a somewhat reasonable rating value */
-	clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
+	clocksource_mips.rating = 200;
+	clocksource_mips.rating += clamp(mips_hpt_frequency / 10000000, 0, 99);
 
 	/*
 	 * R2 onwards makes the count accessible to user mode so it can be used