[ALSA] es18xx - Add PnP BIOS support

This patch adds PnP BIOS support to es18xx driver. It allows ESS ES18xx sound 
chips integrated in some notebooks (such as DTK FortisPro TOP-5A) that don't 
appear as ISA cards (they aren't recognized by ISA PnP, only by PnP BIOS) 
to 'just work' automatically.
Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>