fs/procfs: Avoid the duplicated 0x prefix in pthread cmdline

like this:
... <pthread> 0x0x341de68c
by removing "0x" from format string

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

fs/procfs/fs_procfsproc.c

@@ -689,7 +689,7 @@ static ssize_t proc_cmdline(FAR struct proc_file_s *procfile,
     {
       FAR struct pthread_tcb_s *ptcb = (FAR struct pthread_tcb_s *)tcb;
 
-      linesize   = snprintf(procfile->line, STATUS_LINELEN, " 0x%p\n",
+      linesize   = snprintf(procfile->line, STATUS_LINELEN, " %p\n",
                             ptcb->arg);
       copysize   = procfs_memcpy(procfile->line, linesize, buffer,
                                  remaining, &offset);