Add empty line in register_read comment

Signed-off-by: Ryan Everett <ryan.everett@arm.com>
diff --git a/library/psa_crypto_slot_management.h b/library/psa_crypto_slot_management.h
index 4c0721d..002429b 100644
--- a/library/psa_crypto_slot_management.h
+++ b/library/psa_crypto_slot_management.h
@@ -154,6 +154,7 @@
  * This function increments the key slot registered reader counter by one.
  * If multi-threading is enabled, the caller must hold the
  * global key slot mutex.
+ *
  * \param[in] slot  The key slot.
  *
  * \retval #PSA_SUCCESS