checkpatch: add --strict test for switch/default missing break

checkpatch: add --strict test for switch/default missing break

switch default case is sometimes written as "default:;".  This can cause
new cases added below the default to be defective.

Suggest adding a break; after empty default cases to avoid fallthrough
defects.

Fixed indentation in the other semicolon test above it.

Suggested-by: Peter Senna Tschudin <[email protected]>
Signed-off-by: Joe Perches <[email protected]>
Cc: Andy Whitcroft <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>