build: link libgstvaapi_parse against codec parser

build: link libgstvaapi_parse against codec parser

GST_CODEC_PARSER_* variables are defined if builtin codec parsers are disabled
when running configure.

Right now, libgstcodecparsers links only to libgstvaapi, but libgstvaapi_parse
need it if builtin codec parsers are disabled.

This patch adds GST_CODEC_PARSER_* variables to libgstvaapi_parse
compilation. If builtin codec parsers are enable, this variable is null, so it
should work using libgstvaapi, as normal.

Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
https://bugzilla.gnome.org/show_bug.cgi?id=754845