feat(fvp): implement platform API for LFA cancel operation

Introduce and implement a stub implementation of `plat_lfa_cancel()`
for the FVP platform. This function will later be expanded to handle
component-specific LFA cancellation logic.

Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: I9690b011313bbe0fd458cbe47f32445f8d2d79fa
2 files changed