target/arm: Make RETA[AB] UNDEF when pauth is not implemented

According to the Arm A-profile A64 Instruction Set Architecture,
RETA[AB] should be decoded as UNDEF if the pauth feature is not
implemented.

We got this right in the initial implementation, but accidentally
dropped the feature-check when we converted these insns to
decodetree.

Cc: [email protected]
Fixes: 0ebbe90 ("target/arm: Convert BRA[AB]Z, BLR[AB]Z, RETA[AB] to decodetree")
Signed-off-by: Solomon Tan <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-id: [email protected]
Signed-off-by: Peter Maydell <[email protected]>
(cherry picked from commit 9a3bf0e0ab628de7051b41a88c4628aa9e4d311b)
Signed-off-by: Michael Tokarev <[email protected]>

Author: wjsota

target/arm/tcg/translate-a64.c

@@ -1821,6 +1821,10 @@ static bool trans_RETA(DisasContext *s, arg_reta *a)
 {
     TCGv_i64 dst;
 
+    if (!dc_isar_feature(aa64_pauth, s)) {
+        return false;
+    }
+
     dst = auth_branch_target(s, cpu_reg(s, 30), cpu_X[31], !a->m);
     gen_a64_set_pc(s, dst);
     s->base.is_jmp = DISAS_JUMP;