There will be more places other than vmbus where we need to calculate
the Hyper-V page PFN from a virtual address, so move virt_to_hvpfn() to
hyperv generic header.
Signed-off-by: NBoqun Feng <boqun.feng@gmail.com>
Reviewed-by: NMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20200916034817.30282-6-boqun.feng@gmail.comSigned-off-by: NWei Liu <wei.liu@kernel.org>