JIT: implement timer support in mtspr

Faster, of course, since we avoid the interpreter, but also means we can
get more a more accurate timer in long blocks by adding the offset from the
start of the block to the retrieved timer. I don't know if this will actually
fix any issues, but it's more correct and a nearly-free improvement.

Source/Core/Core/HW/SystemTimers.cpp

@@ -70,31 +70,6 @@ namespace SystemTimers
 
 static u32 CPU_CORE_CLOCK  = 486000000u;             // 486 mhz (its not 485, stop bugging me!)
 
-/*
-GameCube                   MHz
-flipper <-> ARAM bus:      81 (DSP)
-gekko <-> flipper bus:     162
-flipper <-> 1T-SRAM bus:   324
-gekko:                     486
-
-These contain some guesses:
-Wii                             MHz
-hollywood <-> GDDR3 RAM bus:    ??? no idea really
-broadway <-> hollywood bus:     243
-hollywood <-> 1T-SRAM bus:      486
-broadway:                       729
-*/
-// Ratio of TB and Decrementer to clock cycles.
-// TB clk is 1/4 of BUS clk. And it seems BUS clk is really 1/3 of CPU clk.
-// So, ratio is 1 / (1/4 * 1/3 = 1/12) = 12.
-// note: ZWW is ok and faster with TIMER_RATIO=8 though.
-// !!! POSSIBLE STABLE PERF BOOST HACK THERE !!!
-
-enum
-{
-	TIMER_RATIO = 12
-};
-
 static int et_Dec;
 static int et_VI;
 static int et_SI;