ARM: 7274/1: NUC900: Rename nuc900-audio platform device to nuc900-ac97

This change ensures the platform device name matches nuc900-ac97 platform
driver name.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Wan Zongshun <mcuos.com@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>