Build: Fix warning for accelerator enabled build

Fix the following build warning when crypto accelerator
is present: warning: implicit declaration of function
'crypto_hw_accelerator_huk_derive_key' is invalid in C99,
introduced by commit f41c642.

Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
Change-Id: I3d9e1cbdd94cf19b2080dea90ab717d0648dc706
1 file changed