tcg/ppc: Disable TCG_REG_TB for Power9/Power10

This appears to slightly improve performance on power9/10.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/ppc/tcg-target.c.inc

@@ -83,7 +83,7 @@
 #define TCG_VEC_TMP2    TCG_REG_V1
 
 #define TCG_REG_TB     TCG_REG_R31
-#define USE_REG_TB     (TCG_TARGET_REG_BITS == 64)
+#define USE_REG_TB     (TCG_TARGET_REG_BITS == 64 && !have_isa_3_00)
 
 /* Shorthand for size of a pointer.  Avoid promotion to unsigned.  */
 #define SZP  ((int)sizeof(void *))