target/arm: Reduce dcz_blocksize to uint8_t

This value is only 4 bits wide.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230811214031.171020-2-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu.h

@@ -1074,7 +1074,8 @@ struct ArchCPU {
     bool prop_lpa2;
 
     /* DCZ blocksize, in log_2(words), ie low 4 bits of DCZID_EL0 */
-    uint32_t dcz_blocksize;
+    uint8_t dcz_blocksize;
+
     uint64_t rvbar_prop; /* Property/input signals.  */
 
     /* Configurable aspects of GIC cpu interface (which is part of the CPU) */