checkpatch: fix false positive MISSING_BREAK warnings with --file

Using --file mode can give false positives with MISSING_BREAK
fall-through warnings on simple but long multiple consecutive case
statements.

Look for all lines before a case statement for a switch or a statement
when using --file mode.

Fix a misspelling of preceded while there.

Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>