arm64: zynqmp: Change firmware dependency

In case of mini U-Boot configurations there is no need to enable firmware
driver which just consume space for nothing. That's why add an option to
disable it.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/d439399160ff3374f2b39f54f7dd70fa8c8bfea0.1642162121.git.michal.simek@xilinx.com
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 23d57ca..635cea6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1193,7 +1193,7 @@
 	select DM_SERIAL
 	select DM_SPI if SPI
 	select DM_SPI_FLASH if DM_SPI
-	select FIRMWARE
+	imply FIRMWARE
 	select GICV2
 	select GPIO_EXTRA_HEADER
 	select OF_CONTROL
@@ -1203,7 +1203,7 @@
 	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
+	imply SPL_FIRMWARE if SPL
 	select SPL_SEPARATE_BSS if SPL
 	select SUPPORT_SPL
 	select ZYNQMP_IPI