hv_netvsc: Use HV_HYP_PAGE_SIZE for Hyper-V communication

When communicating with Hyper-V, HV_HYP_PAGE_SIZE should be used since
that's the page size used by Hyper-V and Hyper-V expects all
page-related data using the unit of HY_HYP_PAGE_SIZE, for example, the
"pfn" in hv_page_buffer is actually the HV_HYP_PAGE (i.e. the Hyper-V
page) number.

In order to support guest whose page size is not 4k, we need to make
hv_netvsc always use HV_HYP_PAGE_SIZE for Hyper-V communication.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20200916034817.30282-8-boqun.feng@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>