PowerPC: Add functions to read/write the full timebase value

Allows us to get rid of a silly pointer cast and deduplicate some code
from the front-end when it comes to reading the value.

Source/Core/Core/HW/SystemTimers.cpp

@@ -156,7 +156,7 @@ u32 GetFakeDecrementer()
 void TimeBaseSet()
 {
   CoreTiming::SetFakeTBStartTicks(CoreTiming::GetTicks());
-  CoreTiming::SetFakeTBStartValue(*((u64*)&TL));
+  CoreTiming::SetFakeTBStartValue(PowerPC::ReadFullTimeBaseValue());
 }
 
 u64 GetFakeTimeBase()

Source/Core/Core/PowerPC/Interpreter/Interpreter_SystemRegisters.cpp

@@ -4,8 +4,6 @@
 
 #include "Core/PowerPC/Interpreter/Interpreter.h"
 
-#include <cstring>
-
 #include "Common/Assert.h"
 #include "Common/CommonTypes.h"
 #include "Common/FPURoundMode.h"
@@ -253,12 +251,8 @@ void Interpreter::mfspr(UGeckoInstruction inst)
 
   case SPR_TL:
   case SPR_TU:
-  {
-    // works since we are little endian and TL comes first :)
-    const u64 time_base = SystemTimers::GetFakeTimeBase();
-    std::memcpy(&TL, &time_base, sizeof(u64));
-  }
-  break;
+    PowerPC::WriteFullTimeBaseValue(SystemTimers::GetFakeTimeBase());
+    break;
 
   case SPR_WPAR:
   {

Source/Core/Core/PowerPC/PowerPC.cpp

@@ -349,6 +349,18 @@ void RunLoop()
   Host_UpdateDisasmDialog();
 }
 
+u64 ReadFullTimeBaseValue()
+{
+  u64 value;
+  std::memcpy(&value, &TL, sizeof(value));
+  return value;
+}
+
+void WriteFullTimeBaseValue(u64 value)
+{
+  std::memcpy(&TL, &value, sizeof(value));
+}
+
 void UpdatePerformanceMonitor(u32 cycles, u32 num_load_stores, u32 num_fp_inst)
 {
   switch (MMCR0.PMC1SELECT)

Source/Core/Core/PowerPC/PowerPC.h

@@ -178,6 +178,9 @@ void RunLoop();
 u32 CompactCR();
 void ExpandCR(u32 cr);
 
+u64 ReadFullTimeBaseValue();
+void WriteFullTimeBaseValue(u64 value);
+
 void UpdatePerformanceMonitor(u32 cycles, u32 num_load_stores, u32 num_fp_inst);
 
 // Easy register access macros.