ALSA: au88x0: Fix zero clear of stream->resources

There are a few calls of memset() to stream->resources, but they all
are called in a wrong size, sizeof(unsigned char) * VORTEX_RESOURCE_LAST,
while this field is a u32 array.  This may leave the memories not
zero-cleared.

Fix it by replacing them with a simpler sizeof(stream->resources)
instead.

Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>