libata: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
by explicitly adding a break statement instead of letting the code fall
through to the next case.

Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/ata/libata-eh.c

@@ -2613,6 +2613,7 @@ int ata_eh_reset(struct ata_link *link, int classify,
 			switch (tmp) {
 			case -EAGAIN:
 				rc = -EAGAIN;
+				break;
 			case 0:
 				break;
 			default: