[PATCH] tpm_bios: securityfs error checking fix

These functions return ERR_PTR()s on error, not NULL.

Spotted by Randy.

Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Kylene Jo Hall <kjhall@us.ibm.com>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Acked-by: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>