mke2fs: Add check to make sure inode_size * num_inodes isn't too big

mke2fs: Add check to make sure inode_size * num_inodes isn't too big

A quick patch to sanity check the inode ratio vs the inode size.  In
some cases Lustre users have tried specifying an inode size of 4096
bytes, while keeping an inode ratio of one inode per 4096 bytes.  I'm
sure more people will do this now that large inodes are available in
ext4 and documented in e2fsprogs.

Signed-off-by: Andreas Dilger <adilger@clusterfs.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>