checkpatch: improve space before tab --fix option

checkpatch: improve space before tab --fix option

This test should remove all the spaces before a tab not just one space.

Substitute a tab for each 8 space block before a tab and remove less than
8 spaces before a tab.

This SPACE_BEFORE_TAB test is done after CODE_INDENT.

If there are spaces used at the beginning of a line that should be
converted to tabs, please make sure that the CODE_INDENT test and
conversion is done before this SPACE_BEFORE_TAB test and conversion.

Reported-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>