memory: renesas-rpc-if: fix platform-device leak in error path

commit b452dbf2 upstream.

Make sure to free the flash platform device in the event that
registration fails during probe.

Fixes: ca7d8b98

 ("memory: add Renesas RPC-IF driver")
Cc: stable@vger.kernel.org      # 5.8
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20220303180632.3194-1-johan@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>