ARM: am335x: select DM_GPIO

We are supposed to not add config entries with only "default y"
in board/SoC Kconfig files.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NEnric Balletbo i Serra <enric.balletbo@collabora.com>

arch/arm/Kconfig

@@ -459,6 +459,7 @@ config TARGET_AM335X_SL50
 	select CPU_V7
 	select SUPPORT_SPL
 	select DM
+	select DM_GPIO
 	select DM_SERIAL
 
 config TARGET_BAV335X

board/tcl/sl50/Kconfig

@@ -22,10 +22,4 @@ config CONS_INDEX
 	  board you may want something other than UART0 as for example the IDK
 	  uses UART3 so enter 4 here.
 
-config DM_GPIO
-	default y
-
-config DM_SERIAL
-	default y
-
 endif