Simplify dependency rules, move deps to .PRECIOUS

Makefile

@@ -14,6 +14,9 @@ YAMLS := $(foreach crate, $(CRATES), \
 # Each yaml file in devices/ exactly name-matches an SVD file in svd/
 PATCHED_SVDS := $(patsubst devices/%.yaml, svd/%.svd.patched, $(YAMLS))
 FORMATTED_SVDS := $(patsubst devices/%.yaml, svd/%.svd.formatted, $(YAMLS))
+DEPS := $(patsubst devices/%.yaml, .deps/%.d, $(YAMLS))
+
+.PRECIOUS: $(DEPS)
 
 # Each device will lead to a crate/src/device/mod.rs file
 RUST_SRCS := $(foreach crate, $(CRATES), \
@@ -34,7 +37,7 @@ CHECK_SRCS := $(foreach crate, $(CRATES), \
                           $(wildcard devices/$(crate)*.yaml)))
 
 # Turn a devices/device.yaml and svd/device.svd into svd/device.svd.patched
-svd/%.svd.patched: devices/%.yaml svd/%.svd
+svd/%.svd.patched: devices/%.yaml svd/%.svd .deps/%.d
 	python3 scripts/svdpatch.py $<
 
 svd/%.svd.formatted: svd/%.svd.patched
@@ -100,6 +103,4 @@ clean: clean-rs clean-patch clean-html
 	@mkdir -p .deps
 	python3 scripts/makedeps.py $< > $@
 
-$(PATCHED_SVDS): $(patsubst devices/%.yaml, .deps/%.d, $(YAMLS))
-
 -include .deps/*