target-xtensa: implement CPENABLE and PRID SRs

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/target-xtensa/cpu.h b/target-xtensa/cpu.h
index 474466c..37f8b7f 100644
--- a/target-xtensa/cpu.h
+++ b/target-xtensa/cpu.h
@@ -118,12 +118,14 @@
     DEPC = 192,
     EPS2 = 194,
     EXCSAVE1 = 209,
+    CPENABLE = 224,
     INTSET = 226,
     INTCLEAR = 227,
     INTENABLE = 228,
     PS = 230,
     EXCCAUSE = 232,
     CCOUNT = 234,
+    PRID = 235,
     EXCVADDR = 238,
     CCOMPARE = 240,
 };