crypto: ccree - only try to map auth tag if needed

Make sure to only add the size of the auth tag to the source mapping
for encryption if it is an in-place operation. Failing to do this
previously caused us to try and map auth size len bytes from a NULL
mapping and crashing if both the cryptlen and assoclen are zero.

Reported-by: Geert Uytterhoeven <[e-mail]>
Tested-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Gilad Ben-Yossef <[e-mail]>
Cc: [e-mail] # v4.19+
Signed-off-by: Herbert Xu <[e-mail]>

drivers/crypto/ccree/cc_buffer_mgr.c

···
 	}
 
 	size_to_map = req->cryptlen + areq_ctx->assoclen;
-	if (areq_ctx->gen_ctx.op_type == DRV_CRYPTO_DIRECTION_ENCRYPT)
+	/* If we do in-place encryption, we also need the auth tag */
+	if ((areq_ctx->gen_ctx.op_type == DRV_CRYPTO_DIRECTION_ENCRYPT) &&
+	   (req->src == req->dst)) {
 		size_to_map += authsize;
-
+	}
 	if (is_gcm4543)
 		size_to_map += crypto_aead_ivsize(tfm);
 	rc = cc_map_sg(dev, req->src, size_to_map, DMA_BIDIRECTIONAL,