mtd: rawnand: fsmc: 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: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210305082559.GA137646@embeddedor

drivers/mtd/nand/raw/fsmc_nand.c

@@ -930,6 +930,7 @@ static int fsmc_nand_attach_chip(struct nand_chip *nand)
 				 "Using 4-bit SW BCH ECC scheme\n");
 			break;
 		}
+		break;
 
 	case NAND_ECC_ENGINE_TYPE_ON_DIE:
 		break;