x86/bugs: Make i386 use GENERIC_BUG_RELATIVE_POINTERS

Linus figured less #ifdef is more better and making x86-32 use
GENERIC_BUG_RELATIVE_POINTERS removes one layer of macro magic from
the bug.h bits.

Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>