ASoC: Remove unneeded hw_write initialisation in wm8523

It is not required after commit 8d50e447


"ASoC: Factor out I/O for Wolfson 8 bit data 16 bit register CODECs"

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>