soc: ep93xx: drop reference to removed EP93XX_SOC_COMMON config

Commit 6eab0ce6e1c6 ("soc: Add SoC driver for Cirrus ep93xx") adds the
config EP93XX_SOC referring to the config EP93XX_SOC_COMMON.

Within the same patch series of the commit above, the commit 046322f1e1d9
("ARM: ep93xx: DT for the Cirrus ep93xx SoC platforms") then removes the
config EP93XX_SOC_COMMON. With that the reference to this config is
obsolete.

Simplify the expression in the EP93XX_SOC config definition.

Signed-off-by: Lukas Bulwahn <[e-mail]>
Reviewed-by: Nikita Shubin <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>

drivers/soc/cirrus/Kconfig

···
 	bool "Cirrus EP93xx chips SoC"
 	select SOC_BUS
 	select AUXILIARY_BUS
-	default y if !EP93XX_SOC_COMMON
+	default y
 	help
 	  Enable support SoC for Cirrus EP93xx chips.