drivers: mipi_dsi: mcux: add missing soc.h

It looks like this platform is using soc.h to declare some display APIs,
imxrt_pre/post_init_display_interface(). This likely deserves a better
design, but for now let's fix compiler warnings.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

drivers/mipi_dsi/dsi_mcux.c

@@ -11,6 +11,8 @@
 #include <fsl_clock.h>
 #include <zephyr/logging/log.h>
 
+#include <soc.h>
+
 LOG_MODULE_REGISTER(dsi_mcux, CONFIG_MIPI_DSI_LOG_LEVEL);
 
 #define MIPI_DPHY_REF_CLK DT_INST_PROP(0, dphy_ref_frequency)