ltq-deu: make deu hash lock global and remove md5_hmac_ exports

ltq-deu: make deu hash lock global and remove md5_hmac_ exports

All hash algorithms use the same base IFX_HASH_CON to access the hash unit.
Parallel threads should not be able to call different hash algorithms and
therefor a global lock is required.
Fixed linker warning, that md5_hmac_init, md5_hmac_update and
md5_hmac_final are static export symbols. The export symbols are not
required, because the functions are exposed using shash_alg structure.

Signed-off-by: Daniel Kestrel <kestrel1974@t-online.de>