mke2fs: calculate journal blocks just after fs initialize

mke2fs: calculate journal blocks just after fs initialize

We can calculate journal blocks as soon as blocksize is set.
It will help to figure out wrong journal blocks count earlier.
This will save some un-necessary initialization.

Without patch output =>
mke2fs /dev/sdc1 -J size=1048576
mke2fs 1.42.7 (21-Jan-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
61312 inodes, 244936 blocks
12246 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=251658240
8 block groups
32768 blocks per group, 32768 fragments per group
7664 inodes per group
Superblock backups stored on blocks:
	32768, 98304, 163840, 229376

Allocating group tables: done
Writing inode tables: done

The requested journal size is 268435456 blocks; it must be
between 1024 and 10240000 blocks.  Aborting.

With patch output =>
mke2fs /dev/sdc1 -J size=1048576
mke2fs 1.42.7 (21-Jan-2013)

The requested journal size is 268435456 blocks; it must be
between 1024 and 10240000 blocks.  Aborting.

Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>