btrfs: declare rsv_count as unsigned int instead of int

rsv_count ultimately gets passed to start_transaction() which
now takes an unsigned int as its num_items parameter.
The value of rsv_count should always be positive so declare it
as being unsigned.
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NAlexandru Moise <00moses.alexander00@gmail.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/file.c

@@ -2263,7 +2263,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 	u64 drop_end;
 	int ret = 0;
 	int err = 0;
-	int rsv_count;
+	unsigned int rsv_count;
 	bool same_page;
 	bool no_holes = btrfs_fs_incompat(root->fs_info, NO_HOLES);
 	u64 ino_size;