OSD dependency in the MSP module (compiling without OSD not possible)

[raemin]

Describe the bug
As discussed on discord, there is an OSD depency in the MSP module that prevents to compile emuflight without the OSD feature.

To Reproduce
add to \src\main\target<TARGET>\target.h

#undef USE_OSD

Expected behavior
Compile error on MSP.c

    if (osdWarnGetState(OSD_WARNING_DJI)) {
        sbufWriteString(dst, djiWarningBuffer);
        break;
    }

I managed to make it do with the following hack:

#ifdef USE_OSD
if (osdWarnGetState(OSD_WARNING_DJI)) {
sbufWriteString(dst, djiWarningBuffer);
break;
}
#endif

Additional context
My old DTFc / DOGE F3 flight controller does not have OSD. Current Master does fit nicely in the memory once OSD is removed.