powerpc/40x: Add proper BOOTCFLAGS for cuboot-acadia

The cuboot-acadia.c wrapper can cause assembler errors on some
toolchains due to the lack of the proper BOOTCFLAGS.  This adds
the proper flags for the file.
Signed-off-by: NJosh Boyer <jwboyer@linux.vnet.ibm.com>

arch/powerpc/boot/Makefile

@@ -41,6 +41,7 @@ $(obj)/4xx.o: BOOTCFLAGS += -mcpu=405
 $(obj)/ebony.o: BOOTCFLAGS += -mcpu=405
 $(obj)/cuboot-taishan.o: BOOTCFLAGS += -mcpu=405
 $(obj)/cuboot-katmai.o: BOOTCFLAGS += -mcpu=405
+$(obj)/cuboot-acadia.o: BOOTCFLAGS += -mcpu=405
 $(obj)/treeboot-walnut.o: BOOTCFLAGS += -mcpu=405
 $(obj)/virtex405-head.o: BOOTAFLAGS += -mcpu=405