The kernel only supports gcc 3.2+ now so it doesn't make sense
anymore to explicitely check for options this compiler version
already has.

This actually fixes a bug. The -mprefered-stack-boundary check
never worked because gcc rightly complains

  CC      arch/i386/kernel/asm-offsets.s
cc1: -mpreferred-stack-boundary=2 is not between 4 and 12

We just never saw the error because of cc-options.
I changed it to 4 to actually work.

Tested by compiling i386 and x86-64 defconfig with gcc 3.2.

Should speed up the build time a tiny bit and improve
stack usage on i386 slightly.
Signed-off-by: Andi Kleen <ak@suse.de>