ubifs: journal: Fix error return code in ubifs_jnl_write_inode()

Fix to return a negative error code from the error handling case instead
of 0, as done elsewhere in this function.

Fixes: 9ca2d732

 ("ubifs: Limit number of xattrs per inode")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>