deps/Makefile: Add missing "git fetch" to /update and /clean targets

When the Makefile was modified to use a new tag/hash of a given
repo, the "make update" or "make clean" target will fail as the
new version/tag is not yet known to the local repo, only to the
remote (and hence we need a fetch).

Change-Id: I52c44c744674cd4dab0c85086d68bde6f9be1fca
diff --git a/deps/Makefile b/deps/Makefile
index 5641ebe..626bcc1 100644
--- a/deps/Makefile
+++ b/deps/Makefile
@@ -111,7 +111,7 @@
 	cd $(1) && git remote set-url origin $(2)/$(1) && git fetch
 endif
 ifneq ($$($(1)_HEAD),$($(1)_commit))
-	cd $(1) && git checkout -q -f "$($(1)_commit)"
+	cd $(1) && git fetch && git checkout -q -f "$($(1)_commit)"
 endif
 endif
 
@@ -120,7 +120,7 @@
 ifeq ($$($(1)_MODIFIED),1)
 	@echo "WARNING: $(1) skipped because it contains uncommitted modifications!"
 else
-	cd $(1) && git checkout -q -f "$($(1)_commit)" && git reset --hard
+	cd $(1) && git fetch && git checkout -q -f "$($(1)_commit)" && git reset --hard
 endif
 
 .PHONY: $(1)/distclean