drm/stm: dsi: Rename driver name

Rename the driver name from "dw_mipi_dsi-stm" to
"stm32-display-dsi" for a better readability
in /sys/bus/platform/drivers entries.

Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1509012290-16906-1-git-send-email-philippe.cornu@st.com