[test] Add sfx play sample test

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Fix sfx instrument and sample mapping

When instrument or sample numbers are higher than the number of instruments
or samples in the module, it can be an sfx instrument or sample. Add functions
to map these to the appropriate structures.

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>