target/arm: Report correct syndrome for UNDEFINED AT ops with wrong NSE, NS

R_NYXTL says that these AT insns should be UNDEFINED if they
would operate on an EL lower than EL3 and SCR_EL3.{NSE,NS} is
set to the Reserved {1, 0}. We were incorrectly reporting
them with the wrong syndrome; use CP_ACCESS_TRAP_UNCATEGORIZED
so they are reported as UNDEFINED.

Cc: qemu-stable@nongnu.org
Fixes: 1acd00ef1410 ("target/arm/helper: Check SCR_EL3.{NSE, NS} encoding for AT instructions")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20250130182309.717346-3-peter.maydell@linaro.org

target/arm/helper.c

@@ -3601,7 +3601,7 @@ static CPAccessResult at_e012_access(CPUARMState *env, const ARMCPRegInfo *ri,
      * scr_write() ensures that the NSE bit is not set otherwise.
      */
     if ((env->cp15.scr_el3 & (SCR_NSE | SCR_NS)) == SCR_NSE) {
-        return CP_ACCESS_TRAP;
+        return CP_ACCESS_TRAP_UNCATEGORIZED;
     }
     return CP_ACCESS_OK;
 }