overflow: Remove is_non_negative() and is_negative()

overflow: Remove is_non_negative() and is_negative()

The is_non_negative() and is_negative() function-like macros just
exist as a workaround to silence the -Wtype-limits warning. Now that
this warning is disabled, those two macros have lost their raison
d'être. Remove them.

This reverts commit dc7fe518b049 ("overflow: Fix -Wtype-limits
compilation warnings").

Suggested-by: Nicolas Schier <nsc@kernel.org>
Link: https://lore.kernel.org/all/aUT_yWin_xslnOFh@derry.ads.avm.de
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20251220-remove_wtype-limits-v3-3-24b170af700e@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>