[PATCH] tpm: add cancel function

This patch provides the logic to check if an operation has been canceled while
waiting for the response to arrive.

Signed-off-by: Kylene Hall <kjhall@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>