doxygen: Add crypto headers to Doxygen

Now that cryptography headers are sourced from Mbed Crypto, we need to
tell Doxygen about them, so that it can consider them for inclusion
within Doxygen output.
diff --git a/doxygen/mbedtls.doxyfile b/doxygen/mbedtls.doxyfile
index ce58d6b..0cb092e 100644
--- a/doxygen/mbedtls.doxyfile
+++ b/doxygen/mbedtls.doxyfile
@@ -664,7 +664,7 @@
 # directories like "/usr/src/myproject". Separate the files or directories
 # with spaces.
 
-INPUT                  = ../include input
+INPUT                  = ../include ../crypto/include input
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is
@@ -696,7 +696,12 @@
 # Note that relative paths are relative to the directory from which doxygen is
 # run.
 
-EXCLUDE                =
+EXCLUDE                = \
+                         ../crypto/include/mbedtls/check_config.h \
+                         ../crypto/include/mbedtls/compat-1.3.h \
+                         ../crypto/include/mbedtls/config.h \
+                         ../crypto/include/mbedtls/error.h \
+                         ../crypto/include/mbedtls/version.h \
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or
 # directories that are symbolic links (a Unix file system feature) are excluded