arm-bsp-extras/trusted-firmware-m: Enlarge PS asset size limit for SIE

The maximum asset size of the RSE Protected Storage was exceeded.
Extended the size limit to allow more EFI variables.

4 more EFI variables are introduced for enrolling the 4 authenticated
variables for UEFI Secure Boot.

Signed-off-by: Michael Zhao <michael.zhao2@arm.com>
Signed-off-by: Amr Mohamed <amr.mohamed@arm.com>