[ARM] pxa: register wm8731 explicitly for corgi and poodle

The wm8731 driver has been converted to register using the standard I2C
device registration mechanism so we can now do the registration in the
arch/arm code as normal.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>