KVM: arm64: Do not source virt/lib/Kconfig twice

For ARCH=arm64, virt/lib/Kconfig is sourced twice,
from arch/arm64/kvm/Kconfig and from drivers/vfio/Kconfig.
There is no good reason to parse virt/lib/Kconfig twice.

Commit 2412405b ("KVM: arm/arm64: register irq bypass consumer
on ARM/ARM64") should not have added this 'source' directive.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240204074305.31492-1-masahiroy@kernel.org