InstallSct: Fix allocation of SctFileVolume
InstallSct: Fix allocation of SctFileVolume

Signed-off-by: Brendan Jackman <9a0e2fce45c43ecf5e7457c4f206a85a06aae4fc@arm.com>

tianocore/edk2-test,tianocore/edk2-test,tianocore/edk2-test