UBIFS: fix output format of INUM_WATERMARK

The INUM_WATERMARK is a unsigned 32bit value, `%d' prints it as negatave:
[  103.682255] UBIFS warning (ubi0:0 pid 691): ubifs_new_inode: running out of inode numbers (current 122763, max -256)

Fix it as:
[  154.422940] UBIFS warning (ubi0:0 pid 688): ubifs_new_inode: running out of inode numbers (current 122765, max 4294967040)

Change-Id: I45b42eb93e41b0396aad5c42a57e9f096d29ad77
Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Git-commit: 1a7e985dd1bf5939af0f56bbd6d13d2caf48dd63
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>