Fix `MACHINE_FEATURE` override
When adding the efi as a machine feature for corstone1000-mps3, it
gets overridden due to libc-glibc
The default machine feature needs to be inherited from meta-arm which
includes ts-smm-gateway, ts-se-proxy, and arm-ffa.
And then additionally, include efi for meta-cassini
This would enable Trusted services and ARM-FFA driver on the platform
Signed-off-by: Vikas Katariya vikas.katariya@arm.com