nilfs2: fix typo "numer" -> "number" in alloc.c

Fixes the typo found in a warning message of a persistent object
allocator function.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
index 3f959f1..c2a1387 100644
--- a/fs/nilfs2/alloc.c
+++ b/fs/nilfs2/alloc.c
@@ -425,7 +425,7 @@
 	bitmap = bitmap_kaddr + bh_offset(req->pr_bitmap_bh);
 	if (!nilfs_clear_bit_atomic(nilfs_mdt_bgl_lock(inode, group),
 				    group_offset, bitmap))
-		printk(KERN_WARNING "%s: entry numer %llu already freed\n",
+		printk(KERN_WARNING "%s: entry number %llu already freed\n",
 		       __func__, (unsigned long long)req->pr_entry_nr);
 
 	nilfs_palloc_group_desc_add_entries(inode, group, desc, 1);