preproc: correct the logic in the suppression of preproc errors
preproc: correct the logic in the suppression of preproc errors

The logic for suppressing preprocessor errors was missing an !, which
was present before checkin 215186fe82c461bc1ccef7bed5c1a1a0253bfcc9.

Reported-by: Knut St. Osmundsen <faf3fd3ed24c7f43e965a24b9277814d40cbc1b4@anduin.net>
Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@zytor.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm