KVM: x86: hyper-v: Remove unused inline function kvm_hv_free_pa_page()

There is no caller in tree since introduction in commit b4f69df0 ("KVM:
x86: Make Hyper-V emulation optional")

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Message-ID: <20240803113233.128185-1-yuehaibing@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>