[target] EMAX_F405_ELRS_AIO fix SERIALRX_PROVIDER define

[nerdCopter]

• defining SERIALRX_PROVIDER as CRSF rather than SERIALRX_CRSF breaks compiling (Thanks @haslinghuis !)
• fixes:

In file included from ./src/main/pg/rx.c:29:
./src/main/pg/rx.c: In function 'pgResetFn_rxConfig':
./src/config/configs/EMAX_F405_ELRS_AIO/config.h:82:27: error: 'CRSF' undeclared (first use in this function)
   82 | #define SERIALRX_PROVIDER CRSF
      |                           ^~~~
./src/main/config/config_reset.h:41:9: note: in definition of macro 'RESET_CONFIG_2'
   41 |         __VA_ARGS__                                       \
      |         ^~~~~~~~~~~
./src/main/pg/rx.c:84:30: note: in expansion of macro 'SERIALRX_PROVIDER'
   84 |         .serialrx_provider = SERIALRX_PROVIDER,
      |                              ^~~~~~~~~~~~~~~~~
./src/config/configs/EMAX_F405_ELRS_AIO/config.h:82:27: note: each undeclared identifier is reported only once for each function it appears in
   82 | #define SERIALRX_PROVIDER CRSF
      |                           ^~~~
./src/main/config/config_reset.h:41:9: note: in definition of macro 'RESET_CONFIG_2'
   41 |         __VA_ARGS__                                       \
      |         ^~~~~~~~~~~
./src/main/pg/rx.c:84:30: note: in expansion of macro 'SERIALRX_PROVIDER'
   84 |         .serialrx_provider = SERIALRX_PROVIDER,
      |                              ^~~~~~~~~~~~~~~~~
make[2]: *** [Makefile:454: obj/main/STM32F405_EMAX_F405_ELRS_AIO/pg/rx.o] Error 1
make[2]: *** Waiting for unfinished jobs....
%% (optimised) ./src/main/common/explog_approx.c 
%% (speed optimised) ./src/main/common/filter.c 
make[2]: Leaving directory '/source'
make[1]: *** [Makefile:574: hex] Error 2
make[1]: Leaving directory '/source'
make: *** [mk/config.mk:62: EMAX_F405_ELRS_AIO] Error 2
make failed with 2