1) common initialization for all paths in hpfs_read_inode() taken into
a separate helper (hpfs_init_inode())
	2) hpfs mkdir(),create(),mknod() and symlink() do not bother with
iget() anymore - they call new_inode(), do initializations and insert new
inode into icache.  Handling of OOM failures cleaned up - if we can't
allocate in-core inode, bail instead of corrupting the filesystem.
Allocating in-core inode early also avoids one of the deadlocks here
(hpfs_write_inode() from memory pressure by kmem_cache_alloc() could
deadlock on attempt to lock our directory).
	3) hpfs_write_inode() marks the inode dirty again in case if it
fails to iget() its parent directory.  Again, OOM could trigger fs corruption
here.