fix(st): allow crypto lib compilation in aarch64

Cast len with size_t, as it is unsigned long on Aarch64, and no more
unsigned int. Changing functions prototypes will not help as
.verify_signature awaits an unsigned int for its last parameter.

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Change-Id: I9332fd46301a9653af917802788fd97fe7c8a162
1 file changed