ASoC: ab8500: Inform SoC Core that we have our own I/O arrangements

If codec->control_data is not populated SoC Core assumes we want to
use regmap, which fails catastrophically, as we don't have one:

Unable to handle kernel NULL pointer dereference at virtual address 00000080
pgd = c0004000
[00000080] *pgd=00000000
Internal error: Oops: 17 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 1    Not tainted  (3.5.0-rc6-00884-g0b2419e-dirty #130)
PC is at regmap_read+0x10/0x5c
LR is at hw_read+0x80/0x90
pc : [<c01a91b8>]    lr : [<c0216804>]    psr: 60000013

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>