qemu: add MMIO driver for QFW

Add MMIO driver for QFW.

Note that there is no consumer as of this patch.

Signed-off-by: Asherah Connor <ashe@kivikakk.ee>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 3a254eb..c650471 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -378,6 +378,13 @@
 	  Hidden option to enable PIO QEMU fw_cfg interface. This will be
 	  selected by the appropriate QEMU board.
 
+config QFW_MMIO
+	bool
+	depends on QFW
+	help
+	  Hidden option to enable MMIO QEMU fw_cfg interface. This will be
+	  selected by the appropriate QEMU board.
+
 config I2C_EEPROM
 	bool "Enable driver for generic I2C-attached EEPROMs"
 	depends on MISC