sample/tsm-mr: Use SHA-2 library APIs

sample/tsm-mr: Use SHA-2 library APIs

Given that tsm_mr_sample has a particular set of algorithms that it
wants, just use the library APIs for those algorithms rather than
crypto_shash.  This is more straightforward and more efficient.

This also fixes a bug where this module failed to build if it was
enabled without CRYPTO_HASH happening to be set elsewhere in the
kconfig.  (With the concurrent change to make TSM_MEASUREMENTS stop
selecting CRYPTO, this existing build error would have become easier to
encounter, as well.)  Also, even if it built, crypto_alloc_shash() could
fail at runtime due to the needed algorithms not being available.

The library functions simply use direct linking.  So if it builds, which
it will due to the kconfig options being selected, they are available.

Fixes: f6953f1f9ec4 ("tsm-mr: Add tsm-mr sample code")
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/20260318164233.19800-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>