Fix documentation

Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index cfc969b..17bebf3 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -2912,8 +2912,8 @@
  *                              must be appropriate for the selected
  *                              algorithm and key:
  *                              - The required signature size is
- *                                #PSA_SIGN_OUTPUT_SIZE(key_type, key_bits, \p alg)
- *                                where key_type and key_bits are the type and
+ *                                #PSA_SIGN_OUTPUT_SIZE(\c key_type, \c key_bits, \p alg)
+ *                                where \c key_type and \c key_bits are the type and
  *                                bit-size respectively of key.
  *                              - #PSA_SIGNATURE_MAX_SIZE evaluates to the
  *                                maximum signature size of any supported