X86: Make syscall instructions non-speculative in SE.

src/arch/x86/isa/decoder/one_byte_opcodes.isa

@@ -402,7 +402,8 @@
                 // the first byte.
                 0x5: decode IMMEDIATE {
                     -0x80:
-                         SyscallInst::int80('xc->syscall(Rax)', IsSyscall);
+                         SyscallInst::int80('xc->syscall(Rax)',
+                                 IsSyscall, IsNonSpeculative);
                     default: int_Ib();
                 }
 #endif

src/arch/x86/isa/decoder/two_byte_opcodes.isa

@@ -228,7 +228,8 @@
                     0x1: Inst::SYSCALL_LEGACY();
                 }
 #else
-                0x05: SyscallInst::syscall('xc->syscall(Rax)', IsSyscall);
+                0x05: SyscallInst::syscall('xc->syscall(Rax)',
+                              IsSyscall, IsNonSpeculative);
 #endif
                 0x06: Inst::CLTS();
                 0x07: decode MODE_SUBMODE {
@@ -404,7 +405,8 @@
 #if FULL_SYSTEM
                 0x4: sysenter();
 #else
-                0x4: SyscallInst::sysenter('xc->syscall(Rax)', IsSyscall);
+                0x4: SyscallInst::sysenter('xc->syscall(Rax)',
+                             IsSyscall, IsNonSpeculative);
 #endif
                 0x5: sysexit();
                 0x6: Inst::UD2();