Exclude crypto's oid.h now that it is in mbedtls

Otherwise Doxygen complains about two `\file` with the same name.

This is a temporary exclusion which can be removed once crypto no longer has
an oid.h.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/doxygen/mbedtls.doxyfile b/doxygen/mbedtls.doxyfile
index 6b09ae3..cd52300 100644
--- a/doxygen/mbedtls.doxyfile
+++ b/doxygen/mbedtls.doxyfile
@@ -7,7 +7,9 @@
 EXTRACT_STATIC         = YES
 CASE_SENSE_NAMES       = NO
 INPUT                  = ../include ../tf-psa-crypto/include input ../tf-psa-crypto/drivers/builtin/include ../tests/include/alt-dummy
-EXCLUDE                = ../tf-psa-crypto/drivers/builtin/include/mbedtls/build_info.h
+EXCLUDE                = \
+  ../tf-psa-crypto/drivers/builtin/include/mbedtls/build_info.h \
+  ../tf-psa-crypto/drivers/builtin/include/mbedtls/oid.h
 FILE_PATTERNS          = *.h
 RECURSIVE              = YES
 EXCLUDE_SYMLINKS       = YES