jffs2: Allow setting rp_size to zero during remounting

Set rp_size to zero will be ignore during remounting.

The method to identify whether we input a remounting option of
rp_size is to check if the rp_size input is zero. It can not work
well if we pass "rp_size=0".

This patch add a bool variable "set_rp_size" to fix this problem.

Reported-by: Jubin Zhong <zhongjubin@huawei.com>
Signed-off-by: lizhe <lizhe67@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

cpukit/libfs/src/jffs2/src/jffs2_fs_sb.h

@@ -38,6 +38,7 @@ struct jffs2_mount_opts {
 	 * users. This is implemented simply by means of not allowing the
 	 * latter users to write to the file system if the amount if the
 	 * available space is less then 'rp_size'. */
+	bool set_rp_size;
 	unsigned int rp_size;
 };