staging: android/ram_console: Don't build on arches w/o ioremap

This patch fixes UML build:

    CC      drivers/staging/android/ram_console.o
  drivers/staging/android/ram_console.c: In function
  'ram_console_driver_probe':
  drivers/staging/android/ram_console.c:358:2: error: implicit declaration
  of function 'ioremap' [-Werror=implicit-function-declaration]
  cc1: some warnings being treated as errors
  make[3]: *** [drivers/staging/android/ram_console.o] Error 1
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/Kconfig

@@ -27,6 +27,7 @@ config ANDROID_LOGGER
 
 config ANDROID_RAM_CONSOLE
 	bool "Android RAM buffer console"
+	depends on !S390 && !UML
 	default n
 
 config ANDROID_RAM_CONSOLE_ENABLE_VERBOSE