Makefile: Fix config-devices.mak not regenerated when Kconfig updated

When hw/$DIR/Kconfig is changed, the corresponding generated
hw/$DIR/config-devices.mak is not being updated.
Fix this by including all the hw/*/Kconfig files to the prerequisite
names of the rule generating the config-devices.mak files.

Fixes: e0e312f3 (build: switch to Kconfig)
Reported-by: NPeter Maydell <peter.maydell@linaro.org>
Suggested-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Signed-off-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>

Makefile

@@ -390,7 +390,8 @@ MINIKCONF_ARGS = \
     CONFIG_LINUX=$(CONFIG_LINUX) \
     CONFIG_PVRDMA=$(CONFIG_PVRDMA)
 
-MINIKCONF_INPUTS = $(SRC_PATH)/Kconfig.host $(SRC_PATH)/hw/Kconfig
+MINIKCONF_INPUTS = $(SRC_PATH)/Kconfig.host $(SRC_PATH)/hw/Kconfig \
+                   $(wildcard $(SRC_PATH)/hw/*/Kconfig)
 MINIKCONF = $(PYTHON) $(SRC_PATH)/scripts/minikconf.py \
 
 $(SUBDIR_DEVICES_MAK): %/config-devices.mak: default-configs/%.mak $(MINIKCONF_INPUTS) $(BUILD_DIR)/config-host.mak