drm/msm: add stubs for msm_{perf,rd}_debugfs_cleanup

We now call those two functions even when they are not defined
or declared anywhere because DEBUG_FS is disabled:

drivers/gpu/drm/msm/msm_drv.c: In function 'msm_drm_uninit':
drivers/gpu/drm/msm/msm_drv.c:244:2: error: implicit declaration of function 'msm_perf_debugfs_cleanup';did you mean 'msm_framebuffer_cleanup'? [-Werror=implicit-function-declaration]
drivers/gpu/drm/msm/msm_drv.c:245:2: error: implicit declaration of function 'msm_rd_debugfs_cleanup';did you mean 'msm_framebuffer_cleanup'? [-Werror=implicit-function-declaration]

This adds empty stub implementations for that case.

Fixes: 85eac470 ("drm/msm: Remove msm_debugfs_cleanup()")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170320093936.1255573-1-arnd@arndb.de