drivers: soc: xilinx: fix firmware driver Kconfig dependency

The firmware driver is optional, but the power driver depends on it,
which needs to be reflected in Kconfig to avoid link errors:

aarch64-linux-ld: drivers/soc/xilinx/zynqmp_power.o: in function `zynqmp_pm_isr':
zynqmp_power.c:(.text+0x284): undefined reference to `zynqmp_pm_invoke_fn'

The firmware driver can probably be allowed for compile-testing as
well, so it's best to drop the dependency on the ZYNQ platform
here and allow building as long as the firmware code is built-in.

Fixes: ab272643 ("drivers: soc: xilinx: Add ZynqMP PM driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200408155224.2070880-1-arnd@arndb.deSigned-off-by: Michal Simek <michal.simek@xilinx.com>

drivers/soc/xilinx/Kconfig

@@ -19,7 +19,7 @@ config XILINX_VCU
 
 config ZYNQMP_POWER
 	bool "Enable Xilinx Zynq MPSoC Power Management driver"
-	depends on PM && ARCH_ZYNQMP
+	depends on PM && ZYNQMP_FIRMWARE
 	default y
 	select MAILBOX
 	select ZYNQMP_IPI_MBOX
@@ -35,7 +35,7 @@ config ZYNQMP_POWER
 config ZYNQMP_PM_DOMAINS
 	bool "Enable Zynq MPSoC generic PM domains"
 	default y
-	depends on PM && ARCH_ZYNQMP && ZYNQMP_FIRMWARE
+	depends on PM && ZYNQMP_FIRMWARE
 	select PM_GENERIC_DOMAINS
 	help
 	  Say yes to enable device power management through PM domains