drm/hisilicon: Delete the entire file hibmc_ttm.c

Delete the entire file hibmc_ttm.c. drmm_vram_helper_init() can be
called directly from hibmc_load(). hibmc_dumb_create() and
hibmc_mode_funcs can go to hibmc_drm_drv.c

v2:
change Deletted to Delete

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1607044999-47666-13-git-send-email-tiantao6@hisilicon.com