x86/head: Move early exception panic code into early_fixup_exception()

x86/head: Move early exception panic code into early_fixup_exception()

This removes a bunch of assembly and adds some C code instead.  It
changes the actual printouts on both 32-bit and 64-bit kernels, but
they still seem okay.

Tested-by: Boris Ostrovsky <[email protected]>
Signed-off-by: Andy Lutomirski <[email protected]>
Acked-by: Linus Torvalds <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: KVM list <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: xen-devel <[email protected]>
Link: http://lkml.kernel.org/r/4085070316fc3ab29538d3fcfe282648d1d4ee2e.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>