R5900: use the portable FP control register API

libretro-build-linux-aarch64 and libretro-build-osx-arm64 both die here,
and it is the only error in either job - 154 objects compile before it:

  pcsx2/R5900.cpp:18:10: fatal error: xmmintrin.h: No such file or directory

The include is unconditional, and the only thing it was needed for is the
MXCSR save/restore around the audit path's Execute(). common/FPControl.h
already abstracts exactly that - "MXCSR on x86, and FPCR on AArch64" - and
has a full AArch64 branch, so use GetCurrent()/SetCurrent() instead.

Passing the FPControlRegister rather than its .bitmask keeps this off the
member, which is u32 on x86 and u64 on AArch64. Config.h already includes
common/FPControl.h, so no new include is needed. No x86 behaviour change:
GetCurrent()/SetCurrent() are _mm_getcsr()/_mm_setcsr() there.

pcsx2/R5900.cpp

@@ -15,7 +15,6 @@
 
 
 #include <retro_atomic.h>
-#include <xmmintrin.h>
 #include <cstring> /* memset */
 #include <compat/strl.h>
 
@@ -737,8 +736,8 @@ void ps2_audit_ee_exec(int use_interp, unsigned char* regs_io, unsigned ninstr)
 	}
 	else
 	{
-		const u32 host_csr = _mm_getcsr();
-		_mm_setcsr(EmuConfig.Cpu.FPUFPCR.bitmask);
+		const FPControlRegister host_fpcr = FPControlRegister::GetCurrent();
+		FPControlRegister::SetCurrent(EmuConfig.Cpu.FPUFPCR);
 		/* The exit fires at the first block-boundary event test at or
 		 * beyond nextEventCycle; multi-block programs (branches jump
 		 * between blocks with event tests in between) need a cycle
@@ -746,7 +745,7 @@ void ps2_audit_ee_exec(int use_interp, unsigned char* regs_io, unsigned ninstr)
 		Cpu->ExitExecution();
 		cpuRegs.nextEventCycle = cpuRegs.cycle + ninstr * 2 + 64;
 		Cpu->Execute();
-		_mm_setcsr(host_csr);
+		FPControlRegister::SetCurrent(host_fpcr);
 	}
 	cpuRegs.pc = old_pc;
 	cpuRegs.nextEventCycle = old_cycle_target;