Makefile: Fix incorrect FORCE deps on env rules

These rules run on every build even if nothing has changed. The FORCE
dependency is only needed for if_changed, not for cmd. Drop it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index 3f5249c..65098ad 100644
--- a/Makefile
+++ b/Makefile
@@ -1812,7 +1812,7 @@
 		rm -f $@; \
 		touch $@ ; \
 	fi
-include/generated/env.in: include/generated/env.txt FORCE
+include/generated/env.in: include/generated/env.txt
 	$(call cmd,gen_envp)
 
 # Regenerate the environment if it changes
@@ -1830,7 +1830,7 @@
 		touch $@ ; \
 	fi
 
-include/generated/env.txt: $(wildcard $(ENV_FILE)) FORCE
+include/generated/env.txt: $(wildcard $(ENV_FILE))
 	$(call cmd,envc)
 
 # Write out the resulting environment, converted to a C string