kbuild: clean up i386 subarch build

These O_TARGETs keep coming back ;)

arch/i386/mach-generic/Makefile

 #
 # Makefile for the linux kernel.
 #
-# Note! Dependencies are done automagically by 'make dep', which also
-# removes any old dependencies. DON'T put your own dependencies here
-# unless it's something special (ie not a .c file).
-#
-# Note 2! The CFLAGS definitions are now in the main makefile...
 
 EXTRA_CFLAGS	+= -I../kernel
-export-objs     := 
 
 obj-y				:= setup.o
 

arch/i386/mach-visws/Makefile

 #
 # Makefile for the linux kernel.
 #
-# Note! Dependencies are done automagically by 'make dep', which also
-# removes any old dependencies. DON'T put your own dependencies here
-# unless it's something special (ie not a .c file).
-#
-# Note 2! The CFLAGS definitions are now in the main makefile...
-
-.S.o:
-	$(CC) $(AFLAGS) -traditional -c $< -o $*.o
-
-all: mach-visws.o
 
-O_TARGET 	:= mach-visws.o
 EXTRA_CFLAGS	+= -I../kernel
-export-objs     := 
 
 obj-y				:= setup.o traps.o