ANDROID: goldfish_pipe: fix allmodconfig build

tree:   https://android.googlesource.com/kernel/common android-4.4
head:   6297c6ba0d217d5b0998738fbfaff2f04cad77e6
commit: bc43565e1ac5ba3f204886a2275726bb4c3d44e6 [18/20] ANDROID:
goldfish_pipe: An implementation of more parallel pipe
config: i386-randconfig-s1-201646 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        git checkout bc43565e1ac5ba3f204886a2275726bb4c3d44e6
        # save the attached .config to linux build tree
        make ARCH=i386

All errors (new ones prefixed by >>):

>> ERROR: "goldfish_pipe_device_deinit_v1" [drivers/platform/goldfish/goldfish_pipe_v2.ko] undefined!
>> ERROR: "goldfish_pipe_device_init_v1" [drivers/platform/goldfish/goldfish_pipe_v2.ko] undefined!
>> ERROR: "pipe_dev" [drivers/platform/goldfish/goldfish_pipe.ko] undefined!

Change-Id: Ibd51441edf82e6bb6824acc05ea795570cc374e8