docs: Make HTML checks reliable

Fail the QLogic documentation check when tidy is unavailable or any
HTML file does not validate. Mark both HTML check targets as phony so
a file named check cannot silently suppress validation.

qla2x00t/doc/Makefile

@@ -1,2 +1,12 @@
 check:
-	find -name '*.html' | while read f; do tidy -e < "$$f" | sed "s|^-e|$$f|"; done
+	@command -v tidy >/dev/null 2>&1 || { \
+		echo "Error: tidy is required to check the documentation." >&2; \
+		exit 1; \
+	}
+	@status=0; \
+	for f in $$(find . -name '*.html'); do \
+		tidy -e "$$f" || status=$$?; \
+	done; \
+	exit $$status
+
+.PHONY: check

www/Makefile

@@ -8,3 +8,5 @@ check:
 		tidy -e "$$f" || status=$$?; \
 	done; \
 	exit $$status
+
+.PHONY: check