KVM: arm64: nv: Remove dead code from ERET handling

Cleanly, this code cannot trigger, since we filter this from the
caller. Drop it.

Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250514103501.2225951-16-maz@kernel.org


Signed-off-by: Marc Zyngier <maz@kernel.org>