rss: Update model params to support latest RSS

This patch makes the following changes to the model arguments:
- SIC_AUTH_ENABLE/SIC_DECRYPT_ENABLE - these allow the RSS to use
authentication in the SIC (which is used when the XIP flag is set as is
now the case for all TC platforms)
- VMADDRWIDTH=16 - this specifies that the size of the RSS SRAM is 64KiB
which matches the RSS source code expectation (again with the XIP flag
enabled)

Signed-off-by: Jackson Cooper-Driver <jackson.cooper-driver@arm.com>