Sort properly the headers
While here space/tabs cleanup

Reviewed by:	kib
Check for the cross-device cross-link attempt in the VFS, instead of
forcing filesystem VOP_LINK() methods to repeat the code.  In
tmpfs_link(), remove redundand check for the type of the source,
already done by VFS.

Note that NFS server already performs this check before calling
VOP_LINK().

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Remove unused header.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Do not ignore error from tmpfs_alloc_vp().  It results in access to
the random memory.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks