lcd_bus: include dsi_bus.h only on ESP-IDF builds

#16 added `#include "dsi_bus.h"` to modlcd_bus.c unconditionally, but
the header only exists under esp32_include/, which only the ESP32
CMake build puts on the include path. The unix, macOS and web builds
(micropython.mk adds only common_include and sdl_bus) therefore stop
at the qstr step:

  modlcd_bus.c:9:10: fatal error: 'dsi_bus.h' file not found

The DSIBus registration in the module table was already guarded with
`defined(ESP_IDF_VERSION) && SOC_MIPI_DSI_SUPPORTED`; the include now
gets the matching ESP_IDF_VERSION guard.

Checked: preprocessing modlcd_bus.c with the unix port's flags fails
with the error above before this change and succeeds after it. An
ESP32-P4 build still registers DSIBus (mp_lcd_dsi_bus_type and the
DSIBus qstr are in the image), and its firmware differs from the
unguarded build only in the embedded build timestamp and checksums.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: bitcoin3us

ext_mod/lcd_bus/modlcd_bus.c

@@ -6,7 +6,10 @@
 #include "i2c_bus.h"
 #include "i80_bus.h"
 #include "rgb_bus.h"
-#include "dsi_bus.h"
+
+#ifdef ESP_IDF_VERSION
+    #include "dsi_bus.h"
+#endif
 
 #ifdef MP_PORT_UNIX
     #include "sdl_bus.h"