target/loongarch: Implement LSX fpu arith instructions

This patch includes:
- VF{ADD/SUB/MUL/DIV}.{S/D};
- VF{MADD/MSUB/NMADD/NMSUB}.{S/D};
- VF{MAX/MIN}.{S/D};
- VF{MAXA/MINA}.{S/D};
- VFLOGB.{S/D};
- VFCLASS.{S/D};
- VF{SQRT/RECIP/RSQRT}.{S/D}.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20230504122810.4094787-34-gaosong@loongson.cn>

target/loongarch/cpu.h

@@ -55,6 +55,10 @@ FIELD(FCSR0, CAUSE, 24, 5)
     do { \
         (REG) = FIELD_DP32(REG, FCSR0, CAUSE, V); \
     } while (0)
+#define UPDATE_FP_CAUSE(REG, V) \
+    do { \
+        (REG) |= FIELD_DP32(0, FCSR0, CAUSE, V); \
+    } while (0)
 
 #define GET_FP_ENABLES(REG)    FIELD_EX32(REG, FCSR0, ENABLES)
 #define SET_FP_ENABLES(REG, V) \