fix build errors using gcc-4.7

Error: selected processor does not support ARM mode smc #0
error: DIV usage mismatch between arch/arm/boot/compressed/head.o and output
error: DIV usage mismatch between arch/arm/boot/compressed/misc.o and output
error: DIV usage mismatch between arch/arm/boot/compressed/decompress.o and output
error: DIV usage mismatch between arch/arm/boot/compressed/lib1funcs.o and output
error: DIV usage mismatch between arch/arm/boot/compressed/ashldi3.o and output
Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>