In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.
Addresses-Coverity-ID: 
1369526 ("Missing break in switch")
Addresses-Coverity-ID: 
1369529 ("Missing break in switch")
Addresses-Coverity-ID: 
1451415 ("Missing break in switch")
Addresses-Coverity-ID: 115103 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
                        /* up to 3 channels for capture */
                        return -EINVAL;
                link_mask |= 1 << 4;
+               /* fall through */
        case 4:
                if (stream == SNDRV_PCM_STREAM_CAPTURE)
                        /* up to 3 channels for capture */
                        return -EINVAL;
                link_mask |= 1 << 3;
+               /* fall through */
        case 3:
                link_mask |= 1 << 2;
+               /* fall through */
        case 2:
                link_mask |= 1 << 1;
+               /* fall through */
        case 1:
                link_mask |= 1 << 0;
                break;