misc: easelcomm: Fix memory leak in easelcomm scatterlist

1. easelcomm_hw_build_scatterlist() allocates the sglocaldata, but
   it was not freed in easelcomm_hw_destroy_scatterlist().
2. Added kfree to prevent memory leak of "struct sg_local_data"
3. It leaked 13 KB on both AP and easel kernel memory per shot. (128
   bytes per dma transfer, 103 occurrence per shot in burst_process.)

Bug: 79539939
Change-Id: I71b49a362b1c4c2108979286efb600c4a8ff667a
Signed-off-by: Richard Hsu <hsuy@google.com>

drivers/misc/google-easel-comm-hw.c

@@ -534,6 +534,7 @@ void easelcomm_hw_destroy_scatterlist(void *sglocaldata)
 			/* Release sgl retrieved from dma_buf framework */
 			mnh_sg_release_from_dma_buf(sg_local_data);
 		}
+		kfree(sg_local_data);
 	}
 }
 EXPORT_SYMBOL(easelcomm_hw_destroy_scatterlist);

drivers/misc/google-easel-comm-private.h

@@ -44,11 +44,21 @@ enum easelcomm_msg_type {
  * transfer have default values for these.
  */
 struct easelcomm_dma_xfer_info {
-	/* The local MNH driver scatter-gather list, or NULL if discarding */
+	/*
+	 * The local MNH driver scatter-gather list, or NULL if discarding.
+	 * This points to an array of mnh_sg_entry.  Content of this is
+	 * to be used to combine with remote scatter-gather list to be a
+	 * DMA Linked List.
+	 */
 	void *sg_local;
 	/* Size in bytes of the local scatter-gather list, zero if discard */
 	uint32_t sg_local_size;
-	/* Local data private to the MNH layer associated with the SG list */
+	/*
+	 * Local data private to the MNH layer associated with the SG list.
+	 * This points to mnh_sg_list.  It marks information of
+	 * the buffer for DMA transfer, and is used to collect local MNH
+	 * driver scatter-gather list (sg_local).
+	 */
 	void *sg_local_localdata;
 	/*
 	 * Easel/server keeps the remote scatter-gather list received from the