amdvi_cmp_wait: gcc complained about a malformed string behind an ifdef.

struct amdvi_dte: widen the type of the first reserved bitfield so that the packed representation would not cross an alignment boundary for that type. Apparently that causes in-tree gcc (4.2) to insert padding (despite packed, resulting in a wrong structure definition), and causes more modern gcc to emit a warning.

ivrs_hdr_iterate_tbl: delete a misleading check about header length being less than 0 (the type is unsigned) and replace it with a check that the length doesn't exceed the table size.