tpm: Add TPM command library

TPM command library implements a subset of TPM commands defined in TCG
Main Specification 1.2 that are useful for implementing secure boot.
More TPM commands could be added out of necessity.

You may exercise these commands through the 'tpm' command.  However, the
raw TPM commands are too primitive for writing secure boot in command
interpreter scripts; so the 'tpm' command also provides helper functions
to make scripting easier.

For example, to define a counter in TPM non-volatile storage and
initialize it to zero:

$ tpm init
$ tpm startup TPM_ST_CLEAR
$ tpm nv_define d 0x1001 0x1
$ tpm nv_write d 0x1001 0

And then increment the counter by one:

$ tpm nv_read d 0x1001 i
$ setexpr.l i $i + 1
$ tpm nv_write d 0x1001 $i

Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>