util/uut/cmd.c: Use PRIu32 as conversion specifier for uint32_t

[szsam]

If using '%lu', the argument should be of type 'unsigned long', but the actual argument resp_num is of type 'uint32_t'. Calling a printf-like function with the wrong type of arguments causes unpredictable behavior.

Also, use PRIX8 to print uint8_t.