[POWERPC] Remove the unused HTDMSOUND driver

Recently, someone fixed a syntax error in the HTDMSOUND driver
introduced 4 years ago.

Unfortunately not by trying to compile this driver for his hardware but
by code inspection - which seems to be a strong indication that there
are no users left for this OSS sound driver.

This patch therefore removes it.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Dan Malek <dan@embeddedalley.com>
Acked-by: Marcelo Tosatti <marcelo@kvack.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>