PS3: Fix build with 32-bit toolchains

The PS3 bootwrapper files use instructions only available on 64-bit CPUs.
Add the code generation directive '.machine "ppc64"' for toolchains
configured for 32-bit CPUs.

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>