arm-auto-solutions/classes: Use MbedTLS for parsec-service for RD-Aspen

By setting VIRTUAL-RUNTIME_security_provider to "sw-provider"
for fvp-rd-aspen, parsec-service will be configured to use MbedTLS
instead of Trusted Services.

This is temporary until Trusted Services is fully supported on
RD-Aspen.

Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>