ASoC: PXA: Fix codec address on Zipit Z2

WM8750 address is 0x1b, not 0x1a. Without this fix ALSA detects no sound
cards on Zipit

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Acked-by: Marek Vasut <marek.vasut@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>