In preparation to enable -Wimplicit-fallthrough for Clang, fix multiple
warnings by explicitly adding a couple break statements and replacing /*
fall through */ comments with the new pseudo-keyword macro fallthrough;
instead of just letting the code fall through to the next case.

Notice that Clang doesn't recognize /* fall through */ comments as implicit
fall-through markings.

Link: https://github.com/KSPP/linux/issues/115
Link: https://lore.kernel.org/r/2ae1cafd858238b85fc5e7fe5cc183843e21ec9f.1605896059.git.gustavoars@kernel.orgSigned-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>