target/mips: Add CP0 Config0 register definitions for MIPS3 ISA

The MIPS3 and MIPS32/64 ISA use different definitions
for the CP0 Config0 register.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20201201132817.2863301-2-f4bug@amsat.org>

target/mips/cpu.h

@@ -828,7 +828,7 @@ struct CPUMIPSState {
 #define CP0EBase_WG 11
     target_ulong CP0_CMGCRBase;
 /*
- * CP0 Register 16
+ * CP0 Register 16 (after Release 1)
  */
     int32_t CP0_Config0;
 #define CP0C0_M    31
@@ -845,6 +845,14 @@ struct CPUMIPSState {
 #define CP0C0_VI   3
 #define CP0C0_K0   0     /*  2..0  */
 #define CP0C0_AR_LENGTH 3
+/*
+ * CP0 Register 16 (before Release 1)
+ */
+#define CP0C0_Impl 16    /* 24..16 */
+#define CP0C0_IC   9     /* 11..9 */
+#define CP0C0_DC   6     /*  8..6 */
+#define CP0C0_IB   5
+#define CP0C0_DB   4
     int32_t CP0_Config1;
 #define CP0C1_M    31
 #define CP0C1_MMU  25    /* 30..25 */