mke2fs: automatically use 256 byte inodes if project feature enabled

mke2fs: automatically use 256 byte inodes if project feature enabled

If the inode size is not implicitly requested on the command line, and
it is too small to support the project feature, automatically promote
the inode size to be 256 bytes so that the project feature will work.

Note the previous test to check for a too-small inode size didn't work
because it checked before inode size was set in fs_param.  Hence, it
was possible to create file systems with a 128 byte inode and the
project feature enabled.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>