These files are copied by accident and then discovered by shellcheck.

Shellcheck complained about returning -1 because that's essentially 255.

This was required for shellsheck.

The startup file rc.board is copied to the build/../genromfs folder
after the pruning of the files happened. Thus, about 2000 bytes of
comments and whitespace were included in the ROMFS.

This commit moves pruning of the files in ROMFS to a separate cmake
custom command which happens after the ROMFS files have been copied and
the extra files have been added.

Testing showed that this change only affected the rc.board file as
expected.

tone_alarm was started before the parameters were loaded, and the first
tune was played before that as well. CBRK_BUZZER was then read as default,
ignoring the user-configured value.

We now start tone_alarm after we load the parameters. Note that a
previously published startup tone or SD card error will still be played.

   Delete auto generated vars, and others that were missed.

Keeps things more modular.

* added a parameter for enabled the smart battery
* start tel1 and tel2 at 921600 and max rate
* turned up the max tx rate on mavlink streams for telem1 and telem2
* turned off mavlink stream for tel1 in 4250_teal. This is connected to TX1 FTDI UART and has issues.
* moved check to 4250 board ID to start mpu9250s for Teal airframe into fmuv4 rc.board.

 - fixes #10980

* Integrated preliminary ICM20948 support into MPU9250 driver.
Fixed temperature conversion for MPU9250/ICM20948.
* Included missing check for PX4_I2C_OBDEV_MPU9250 in main.cpp.
* Added explicit bus for internal MPU9250 on Pixhawk 2.1 to avoid implicit start
of an externally attached device with wrong orientation.

 - fixes #10972

Co-Authored-By: CUAVcaijie <caijie@cuav.net>