Staging: hv: remove function pointer typedefs from VmbusApi.h

function pointer typedefs are allowed in the kernel, but only if they
make sense, which they really do not here, as they are not passed around
with any kind of frequency.  So just spell them all out, it makes the
code smaller and easier to understand overall.

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