raw/skeleton: fix warnings with GCC 9
raw/skeleton: fix warnings with GCC 9

GCC9 gives warnings if the parameter passed to printf for "%s" could be
NULL, so we need to add checks in some cases to ensure that is not the
case.

Fixes: 61c592a8d035 ("raw/skeleton: introduce skeleton rawdev driver")
Cc: stable@dpdk.org

Signed-off-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk