ext2fs: make e2fs_maxcontig local and remove tautological check.

ext2fs: make e2fs_maxcontig local and remove tautological check.

e2fs_maxcontig was modelled after UFS when bringing the
"Orlov allocator" to ext2. On UFS fs_maxcontig is kept in the
superblock and is used by userland tools (fsck and growfs),

In ext2 this information is volatile so it is not available
for userland tools, so in this case it doesn't have sense
to carry it in the in-memory superblock.

Also remove a pointless check for MAX(1, x) > 0.

Submitted by:	Christoph Mallon
MFC after:	2 weeks