vxge: avoid -Wemtpy-body warnings

There are a few warnings about empty debug macros in this driver:

drivers/net/ethernet/neterion/vxge/vxge-main.c: In function 'vxge_probe':
drivers/net/ethernet/neterion/vxge/vxge-main.c:4480:76: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
 4480 |                                 "Failed in enabling SRIOV mode: %d\n", ret);

Change them to proper 'do { } while (0)' expressions to make the
code a little more robust and avoid the warnings.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>