[PATCH] tpm: read return code issue

Replace an erroneous return code for the read function when no data is
available.

Signed-of-by: Kylene Hall <kjhall@us.ibm.com>

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>