ARM: ux500: Fix unmet direct dependency

A recent change to a Kconfig configuration saw MACH_U8500
remove TPS6105X selection. In doing so Kconfig stopped
selecting REGULATORS, which is still required. This patch
sees UX500_SOC_DB8500 explicitly select it instead.
Signed-off-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

arch/arm/mach-ux500/Kconfig

@@ -17,6 +17,7 @@ config UX500_SOC_DB5500
 config UX500_SOC_DB8500
 	bool
 	select MFD_DB8500_PRCMU
+	select REGULATOR
 	select REGULATOR_DB8500_PRCMU
 	select CPU_FREQ_TABLE if CPU_FREQ