Follow up on "Treble HAL interfaces for drm+crypto"

Responding to post-submit feedback on previous CL.

b/32815560

Change-Id: Iaf412dc5c39c0595a0486a1220caf4e1c844e824
Tests: Make completes successfully
diff --git a/drm/crypto/1.0/ICryptoFactory.hal b/drm/crypto/1.0/ICryptoFactory.hal
index 58f86df..c1ff31f 100644
--- a/drm/crypto/1.0/ICryptoFactory.hal
+++ b/drm/crypto/1.0/ICryptoFactory.hal
@@ -25,7 +25,7 @@
  * which are used by a codec to decrypt protected video content.
  */
 interface ICryptoFactory {
-    /*
+    /**
      * Determine if a crypto scheme is supported by this HAL
      *
      * @param uuid identifies the crypto scheme in question
@@ -33,20 +33,21 @@
      */
     isCryptoSchemeSupported(uint8_t[16] uuid) generates(bool isSupported);
 
-    /*
+    /**
      * Create a crypto plugin for the specified uuid and scheme-specific
      * initialization data.
      *
      * @param uuid uniquely identifies the drm scheme. See
      * http://dashif.org/identifiers/protection for uuid assignments
      * @param initData scheme-specific init data.
-     * @return the status of the call
-     * @return the created ICryptoPlugin
-    */
+     * @return status the status of the call. If the plugin can't
+     * be created, the HAL implementation must return ERROR_DRM_CANNOT_HANDLE.
+     * @return cryptoPlugin the created ICryptoPlugin
+     */
     createPlugin(uint8_t[16] uuid, vec<uint8_t> initData)
         generates (Status status, ICryptoPlugin cryptoPlugin);
 
-    /*
+    /**
      * Destroy a previously created crypto plugin
      *
      * @return status the status of the call