checkpatch: improve macro reuse test

checkpatch: improve macro reuse test

checkpatch reports a false positive when using token pasting argument
multiple times in a macro.

Fix it.

Miscellanea:

o Make the $tmp variable name used in the macro argument tests
  a bit more descriptive

Link: http://lkml.kernel.org/r/cf434ae7602838388c7cb49d42bca93ab88527e7.1498483044.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>