Automatically pick up all Markdown files

Assume GNU make. We already do with the toplevel makefile.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/docs/architecture/Makefile b/docs/architecture/Makefile
index 6252ab0..5bee504 100644
--- a/docs/architecture/Makefile
+++ b/docs/architecture/Makefile
@@ -2,20 +2,7 @@
 
 default: all
 
-all_markdown = \
-               alternative-implementations.md \
-               mbed-crypto-storage-specification.md \
-               psa-crypto-implementation-structure.md \
-               psa-migration/psa-limitations.md \
-               psa-migration/strategy.md \
-               psa-migration/tasks-g2.md \
-               psa-migration/testing.md \
-               testing/driver-interface-test-strategy.md \
-               testing/invasive-testing.md \
-               testing/psa-storage-format-testing.md \
-               testing/test-framework.md \
-               tls13-support.md \
-	       # This line is intentionally left blank
+all_markdown = $(wildcard *.md */*.md)
 
 html: $(all_markdown:.md=.html)
 pdf: $(all_markdown:.md=.pdf)