x86: Fix the flag handling code in FABS and FCHS

This changeset fixes two problems in the FABS and FCHS
implementation. First, the ISA parser expects the assignment in
flag_code to be a pure assignment and not an and-assignment, which
leads to the isa_parser omitting the misc reg update. Second, the FCHS
and FABS macro-ops don't set the SetStatus flag, which means that the
default micro-op version, which doesn't update FSW, is executed.

src/arch/x86/isa/insts/x87/arithmetic/change_sign.py

@@ -38,10 +38,10 @@
 microcode = '''
 
 def macroop FABS {
-    absfp st(0), st(0)
+    absfp st(0), st(0), SetStatus=True
 };
 
 def macroop FCHS {
-    chsfp st(0), st(0)
+    chsfp st(0), st(0), SetStatus=True
 };
 '''

src/arch/x86/isa/microops/fpop.isa

@@ -365,9 +365,9 @@ let {{
 
     class absfp(FpUnaryOp):
         code = 'FpDestReg = fabs(FpSrcReg1);'
-        flag_code = 'FSW &= (~CC1Bit);'
+        flag_code = 'FSW = FSW & (~CC1Bit);'
 
     class chsfp(FpUnaryOp):
         code = 'FpDestReg = (-1) * (FpSrcReg1);'
-        flag_code = 'FSW &= (~CC1Bit);'
+        flag_code = 'FSW = FSW & (~CC1Bit);'
 }};