KVM: Remove unused kvm_device_{get,put}() declarations

Commit 07f0a7bd ("kvm: destroy emulated devices on VM exit") removed the
functions but not these declarations.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20230814140339.47732-1-yuehaibing@huawei.com


[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>