selftests/xsk: Increase chars for interface name to 16

So that "enp240s0f0" or such name can be used against xskxceiver.
While at it, also extend character count for netns name.
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20220901114813.16275-4-maciej.fijalkowski@intel.com

tools/testing/selftests/bpf/xskxceiver.h

@@ -29,8 +29,8 @@
 #define TEST_FAILURE -1
 #define TEST_CONTINUE 1
 #define MAX_INTERFACES 2
-#define MAX_INTERFACE_NAME_CHARS 7
-#define MAX_INTERFACES_NAMESPACE_CHARS 10
+#define MAX_INTERFACE_NAME_CHARS 16
+#define MAX_INTERFACES_NAMESPACE_CHARS 16
 #define MAX_SOCKETS 2
 #define MAX_TEST_NAME_SIZE 32
 #define MAX_TEARDOWN_ITER 10