virtchnl: Add missing padding to virtchnl_proto_hdrs

On m68k (Coldfire M547x):

      CC      drivers/net/ethernet/intel/i40e/i40e_main.o
    In file included from drivers/net/ethernet/intel/i40e/i40e_prototype.h:9,
		     from drivers/net/ethernet/intel/i40e/i40e.h:41,
		     from drivers/net/ethernet/intel/i40e/i40e_main.c:12:
    include/linux/avf/virtchnl.h:153:36: warning: division by zero [-Wdiv-by-zero]
      153 |  { virtchnl_static_assert_##X = (n)/((sizeof(struct X) == (n)) ? 1 : 0) }
	  |                                    ^
    include/linux/avf/virtchnl.h:844:1: note: in expansion of macro ‘VIRTCHNL_CHECK_STRUCT_LEN’
      844 | VIRTCHNL_CHECK_STRUCT_LEN(2312, virtchnl_proto_hdrs);
	  | ^~~~~~~~~~~~~~~~~~~~~~~~~
    include/linux/avf/virtchnl.h:844:33: error: enumerator value for ‘virtchnl_static_assert_virtchnl_proto_hdrs’ is not an integer constant
      844 | VIRTCHNL_CHECK_STRUCT_LEN(2312, virtchnl_proto_hdrs);
	  |                                 ^~~~~~~~~~~~~~~~~~~

On m68k, integers are aligned on addresses that are multiples of two,
not four, bytes.  Hence the size of a structure containing integers may
not be divisible by 4.

Fix this by adding explicit padding.

Fixes: 1f7ea1c ("ice: Enable FDIR Configure for AVF")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

include/linux/avf/virtchnl.h

@@ -830,6 +830,7 @@ VIRTCHNL_CHECK_STRUCT_LEN(72, virtchnl_proto_hdr);
 
 struct virtchnl_proto_hdrs {
 	u8 tunnel_level;
+	u8 pad[3];
 	/**
 	 * specify where protocol header start from.
 	 * 0 - from the outer layer