tests: Move tests/hex-loader-check-data/ to tests/data/hex-loader/

Currently tests/hex-loader-check-data contains data files used
by the hexloader-test, and configure individually symlinks those
data files into the build directory using a wildcard.

Using a wildcard like this is a bad idea, because if a new
data file is added, nothing causes configure to be rerun,
and so no symlink is added for the new file. This can cause
tests to spuriously fail when they can't find their data.
Instead, it's better to symlink an entire directory of
data files. We already have such a directory: tests/data.

Move the data files from tests/hex-loader-check-data/ to
tests/data/hex-loader/, and remove the unnecessary symlinking.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>