RM] 3025/1: Add I2S platform device for PXA

Patch from Matt Reimer

Adds an I2S platform_device for PXA. I2S is used to interface
with sound chips on systems like iPAQ h1910/h2200/hx4700 and
Asus 716.

Signed-off-by: mreimer@vpop.net
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>