ci: improve clean-git by reseting submodules

This avoids a situation in which `variables.mk` from
`nimbus-build-system` does't exist, but at the same time `git submodule
update` doesn't work due to sumodules stuck in a bad state.

Signed-off-by: Jakub Sokołowski <jakub@status.im>

Makefile

@@ -612,8 +612,9 @@ clean: | clean-common
 	+ $(MAKE) -C vendor/DOtherSide/build --no-print-directory clean
 
 clean-git:
-	git clean -fdx
-	git submodule foreach --recursive git clean -fdx
+	git clean -qfdx
+	git submodule foreach --recursive git reset -q --hard
+	git submodule foreach --recursive git clean -qfdx
 
 force-rebuild-status-go:
 	bash ./scripts/force-rebuild-status-go.sh $(STATUSGO)