rtc: zynqmp: depend on HAS_IOMEM

The Xilinx zynqmp RTC driver makes use of IOMEM functions like
devm_platform_ioremap_resource(), which are only available if
CONFIG_HAS_IOMEM is defined.

This causes the driver not to be enable under make ARCH=um allyesconfig,
even though it won't build.

By adding a dependency on HAS_IOMEM, the driver will not be enabled on
architectures which don't support it.

Fixes: 09ef18bc ("rtc: use devm_platform_ioremap_resource() to simplify code")
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210127035146.1523286-1-davidgow@google.com

drivers/rtc/Kconfig

@@ -1293,7 +1293,7 @@ config RTC_DRV_OPAL
 
 config RTC_DRV_ZYNQMP
 	tristate "Xilinx Zynq Ultrascale+ MPSoC RTC"
-	depends on OF
+	depends on OF && HAS_IOMEM
 	help
 	  If you say yes here you get support for the RTC controller found on
 	  Xilinx Zynq Ultrascale+ MPSoC.