drm/msm/dsi: fix error return code in msm_dsi_host_init()

Fix to return error code -ENOMEM from the malloc error handling
case instead of 0, as done elsewhere in this function.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170209151907.28800-1-weiyj.lk@gmail.com