ERROR: modpost: "mipi_dsi_attach" undefined!

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   3b9cdafb5358eb9f3790de2f728f765fef100731
commit: 23278bf54afe180967069bdc8c0f1c7a365fc63e drm/bridge: Introduce LT9611 DSI to HDMI bridge
date:   7 months ago
config: s390-randconfig-r022-20210223 (attached as .config)
compiler: s390-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=23278bf54afe180967069bdc8c0f1c7a365fc63e
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 23278bf54afe180967069bdc8c0f1c7a365fc63e
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=s390 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: "mipi_dsi_attach" [drivers/gpu/drm/bridge/lontium-lt9611.ko] undefined!
>> ERROR: modpost: "mipi_dsi_device_register_full" [drivers/gpu/drm/bridge/lontium-lt9611.ko] undefined!
>> ERROR: modpost: "of_find_mipi_dsi_host_by_node" [drivers/gpu/drm/bridge/lontium-lt9611.ko] undefined!
>> ERROR: modpost: "mipi_dsi_device_unregister" [drivers/gpu/drm/bridge/lontium-lt9611.ko] undefined!
>> ERROR: modpost: "mipi_dsi_detach" [drivers/gpu/drm/bridge/lontium-lt9611.ko] undefined!

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

Attachment: .config.gz
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