hv: Remove unnecessary comparison of unsigned against 0

pfncount is of type u32 and thus can never be smaller than 0.

Found by the coverity scanner, CID 143213.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>