firmware: omnia-mcu-firmware: Bump to 4.1

firmware: omnia-mcu-firmware: Bump to 4.1

Bump `omnia-mcu-firmware` to version 4.1.

This version fixes the following issue on boards with GD32 MCU:
* the user has old GD32 MCU bootloader and application (version 2.0)
* the user upgraded MCU application firmware to newer version (from
  2.99 to 4.0)
* the user wants to upgrade application again, but it is impossible,
  because when MCU application firmware jumps into the old MCU
  bootloader firmware (2.0), the old bootloader firmware gets stuck in
  exception
* the user has to restart the board and upgrade the bootloader firmware
  first, which is not ideal, since if bootloader firmware upgrade is
  interrupted, the board gets bricked

Therefore the `omnia-mcutool` utility version 0.3-rc3 will refuse to
upgrade MCU application firmware to versions 2.99 to 4.0 if the MCU
bootloader firmware is at version 2.0.

For users to be able to upgrade MCU application firmware on GD32
boards, they will need this new 4.1 version.

Users that already upgraded the MCU application firmware to a version
version between 2.99 and 4.0 (using a previous version of the
`omnia-mcutool` utility) have no other choice but to upgrade MCU
bootloader firmware as well.

Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://github.com/openwrt/openwrt/pull/16159
Signed-off-by: Robert Marko <robimarko@gmail.com>