Staging: hv: remove VmbusGetChannelInfo

It's not needed, make the function pointer point to get_channel_info()
instead.

Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>