video: stm32: remove all child of DSI bridge when its probe failed

Remove the child device of the STM32 DSI bridge when the driver probe
failed to stop futher probe request on panels used with STMicroelectronics
board (orisetech_otm8009a.c or raydium-rm68200.c driver).

This patch avoid the trace "cannot get reset GPIO" when
STM32MP157 device tree is used on stm32MP151 SOC without DSI support.

In this hw_version value is 0, as DSI bridge is absent and the panel
ofdata_to_platdata is called for each try of panel probe,
the gpio reset pin is requested but after dsi father probe failed).

For the next request, the PANEL ofdata_to_platdata failed as the gpio
is already used.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>