selftests/powerpc/ptrace: Fix typo in pid_max search error

pid_max_addr() searches for the 'pid_max' symbol in /proc/kallsyms, and
prints an error if it cannot find it. The error message has a typo,
calling it pix_max.
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230725005841.28854-4-bgray@linux.ibm.com

tools/testing/selftests/powerpc/ptrace/ptrace-perf-hwbreak.c

@@ -46,7 +46,7 @@ static unsigned long pid_max_addr(void)
 		return strtoul(addr, &c, 16);
 	}
 	fclose(fp);
-	printf("Could not find pix_max. Exiting..\n");
+	printf("Could not find pid_max. Exiting..\n");
 	exit(EXIT_FAILURE);
 	return -1;
 }