On top of the previous biarch changes for UML, this makes the preprocessor
changes a bit cleaner. Specify the 64-bit build in CPPFLAGS on the x86_64
SUBARCH, rather than #undef'ing i386. Compile-tested with i386 and x86_64
SUBARCHs.
Signed-off-by: Nishanth Aravamudan
Signed-off-by: Jeff Dike
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds