fs: add i_blocksize()

Replace all 1 << inode->i_blkbits and (1 << inode->i_blkbits) in fs
branch.

This patch also fixes multiple checkpatch warnings: WARNING: Prefer
'unsigned int' to bare use of 'unsigned'

Thanks to Andrew Morton for suggesting more appropriate function instead
of macro.

[geliangtang@gmail.com: truncate: use i_blocksize()]
  Link: http://lkml.kernel.org/r/9c8b2cd83c8f5653805d43debde9fa8817e02fc4.1484895804.git.geliangtang@gmail.com
Link: http://lkml.kernel.org/r/1481319905-10126-1-git-send-email-fabf@skynet.be
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/reiserfs/file.c

@@ -189,7 +189,7 @@ int reiserfs_commit_page(struct inode *inode, struct page *page,
 	int ret = 0;
 
 	th.t_trans_id = 0;
-	blocksize = 1 << inode->i_blkbits;
+	blocksize = i_blocksize(inode);
 
 	if (logit) {
 		reiserfs_write_lock(s);

fs/reiserfs/inode.c

@@ -525,7 +525,7 @@ static int reiserfs_get_blocks_direct_io(struct inode *inode,
 	 * referenced in convert_tail_for_hole() that may be called from
 	 * reiserfs_get_block()
 	 */
-	bh_result->b_size = (1 << inode->i_blkbits);
+	bh_result->b_size = i_blocksize(inode);
 
 	ret = reiserfs_get_block(inode, iblock, bh_result,
 				 create | GET_BLOCK_NO_DANGLE);