Revert "Platform/RaspberryPi: Setup option for disabling Fast Boot"

This reverts commit efdc159e.

This commit is not longer required as Boot Discovery Policy has been
implemented for Raspberry Pi.

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
Reviewed-by: Sunny Wang <sunny.wang@arm.com>
Reviewed-by: Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>
Reviewed-by: Pete Batard <pete@akeo.ie>
Tested-by: Pete Batard <pete@akeo.ie>