ASoC: Ux500: remove test for undefined Kconfig macro

A test for CONFIG_SND_SOC_UX500_AB5500 was added in v3.5. But there
never was a corresponding Kconfig symbol so this test has always
evaluated to true. And since AB5500 support was removed in v3.5 it
appears safe to remove this test and a few lines of code.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>