KVM: arm/arm64: vgic-irqfd: Fix MSI entry allocation

KVM: arm/arm64: vgic-irqfd: Fix MSI entry allocation

commit 150009e2c70cc3c6e97f00e7595055765d32fb85 upstream.

Using the size of the structure we're allocating is a good idea
and avoids any surprise... In this case, we're happilly confusing
kvm_kernel_irq_routing_entry and kvm_irq_routing_entry...

Fixes: 95b110ab9a09 ("KVM: arm/arm64: Enable irqchip routing")
Reported-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>