This reverts commit c8fdd247.

It turns out the kernel was correct, and the gcc complaint was a gcc
bug.  The preferred stack boundary is expressed not in bytes, but in the
the log2() of the preferred boundary, so "-mpreferred-stack-boundary=2"
is in fact exactly what we want, but a gcc that is compiled for x86-64
will consider it an error (because the 64-bit calling sequence says that
the stack should be 16-byte aligned) even if we are then using "-m32" to
generate 32-bit code.
Noted-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: Jan Hubicka <jh@suse.cz>
Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>