ARM: zynqmp: Fix SPL_DM_SPI dependencies

Add missing dependencies for DM_SPI_FLASH.
Kconfig reports it as:
WARNING: unmet direct dependencies detected for SPL_DM_SPI_FLASH
  Depends on [n]: SPL [=n] && SPL_DM [=n]
  Selected by [y]:
  - ARCH_ZYNQMP [=y] && <choice> && SPL_DM_SPI [=y]

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 21c43fa..24202bc 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1152,7 +1152,8 @@
 	select OF_CONTROL
 	select SPL_BOARD_INIT if SPL
 	select SPL_CLK if SPL
-	select SPL_DM_SPI if SPI
+	select SPL_DM if SPL
+	select SPL_DM_SPI if SPI && SPL_DM
 	select SPL_DM_SPI_FLASH if SPL_DM_SPI
 	select SPL_DM_MAILBOX if SPL
 	select SPL_FIRMWARE if SPL