bindesc: Fix placing of the descriptors end tag

Prior to this fix the descriptors end tag was placed in the binary
using LONG. This was wrong because the tag is of type short, and
the size of the descriptor (0), should have also been placed.
It so happened that on little endian machines the incorrect linker
script yielded correct results, as the extra zeros added to make
the value a long ended up as the correct byte sequence
(FF FF 00 00). On big endian machines however, the wrong sequence
is generated (00 00 FF FF).
This patch correct this issue.

Signed-off-by: Yonatan Schachter <yonatan.schachter@gmail.com>