scsi: target: core: Fix fall-through warnings for Clang

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

Link: https://github.com/KSPP/linux/issues/115
Link: https://lore.kernel.org/r/761d6f755e8a6f8a6daebd1e5c1394167e5c780a.1605896059.git.gustavoars@kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_iblock.c

@@ -211,6 +211,7 @@ static unsigned long long iblock_emulate_read_cap_with_block_size(
 			break;
 		case 512:
 			blocks_long <<= 3;
+			break;
 		default:
 			break;
 		}

drivers/target/target_core_pr.c

@@ -337,6 +337,7 @@ static int core_scsi3_pr_seq_non_holder(struct se_cmd *cmd, u32 pr_reg_type,
 	switch (pr_reg_type) {
 	case PR_TYPE_WRITE_EXCLUSIVE:
 		we = 1;
+		fallthrough;
 	case PR_TYPE_EXCLUSIVE_ACCESS:
 		/*
 		 * Some commands are only allowed for the persistent reservation