ARM: dts: stm32: fix dtbs_check warning on ili9341 dts binding on stm32f429 disco

Since the compatible string defined from ilitek,ili9341.yaml is
"st,sf-tc240t-9370-t", "ilitek,ili9341"

so, append "ilitek,ili9341" to avoid the below dtbs_check warning.

arch/arm/boot/dts/stm32f429-disco.dt.yaml: display@1: compatible:
['st,sf-tc240t-9370-t'] is too short

Fixes: a726e2f0 ("ARM: dts: stm32: enable ltdc binding with ili9341, gyro l3gd20 on stm32429-disco board")
Signed-off-by: Dillon Min <dillon.minfei@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>