arm: mach-sc5xx: clean up Kconfig

Moves common options between all SC5xx series boards to the ARCH_SC5XX
option instead of duplicating them.

Also, it was possible to select multiple of the SoC support options.
Given a U-Boot binary can only support a single platform, this moves
the SoC selection to a `choice`, making them mutually exclusive.

Signed-off-by: Oliver Gaskell <Oliver.Gaskell@analog.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ba0359f..7296012 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1868,6 +1868,14 @@
 
 config ARCH_SC5XX
 	bool "Analog Devices SC5XX-processor family"
+	select ADI_SC5XX_TIMER
+	select DM
+	select DM_SERIAL
+	select PANIC_HANG
+	select SPL
+	select SPL_DM
+	select SUPPORT_SPL
+	select TIMER
 
 config TARGET_SL28
 	bool "Support sl28"