ASoC: Fix build dependency for SND_SOC_JZ4740_CODEC

ASoC: Fix build dependency for SND_SOC_JZ4740_CODEC

Currently SND_SOC_JZ4740_CODEC depends on SOC_JZ4740 but SOC_JZ4740 is not
defined in any Kconfig. Thus the codec driver will not be built when select
"Build all ASoC CODEC drivers".
(Unless it is selected by SND_JZ4740_SOC_QI_LB60).
Remove the dependency with SOC_JZ4740, then this code driver can be built when
select "Build all ASoC CODEC drivers".

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>