drm/stm: drv: Rename platform driver name

drm/stm: drv: Rename platform driver name

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

Note: We keep "stm" as drm_driver.name because it is better
when using "modetest -M stm ..." (even if recent modetest patch
avoids using -M).

Signed-off-by: Philippe CORNU <[email protected]>
Reviewed-by: Benjamin Gaignard <[email protected]>
Signed-off-by: Benjamin Gaignard <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]