Forced hash generation used to always generate hash via RSA encryption.
This patch changes encryption based on ARM_ROTPK_LOCATION.
Also removes setting KEY_ALG based on ARM_ROTPL_LOCATION - there is no
relation between these two.

Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>
Change-Id: Id727d2ed06176a243719fd0adfa0cae26c325005