android 内核编译时，编译驱动只生成.o文件，不生成.ko文件，确认驱动没有编译进内核，第一次编译的时候生成过.ko文件，以后在编译时就不生成ko文件了。
Building modules, stage 2.
MODPOST 0 modules
OBJCOPY arch/arm/boot/Image
Kernel: arch/arm/boot/Image is ready
GZIP arch/arm/boot/compressed/piggy.gzip
CC arch/arm/boot/compressed/misc.o
CC arch/arm/boot/compressed/decompress.o
CC arch/arm/boot/compressed/string.o
AS arch/arm/boot/compressed/piggy.gzip.o
LD arch/arm/boot/compressed/vmlinux
OBJCOPY arch/arm/boot/zImage
Kernel: arch/arm/boot/zImage is ready
CAT arch/arm/boot/zImage-dtb
Kernel: arch/arm/boot/zImage-dtb is ready
