How can i extract u-boot image from fgt90d.out firmware and install Openwrt image?

I have a lot of out of licensed Fortigate90D devices so i want to reuse and run Openwrt/pfsense on them.
I have dumped and decoded the bios and got some useful datas,
according to datas we can see u-boot.bin, u-boot.bin.cpu2 and fsoc/spi_boot_fsoc.bin images so i want to know how we can extract these bootloader images and so install custom open source projects like OpenWRT, pfsense.

Any help would be appreciated
thanks..

 no_repeat=1�uart=loadb 100000;go 100000
�mbu=sete tftpip 172.30.80.145;sete myip 172.30.80.154;tftp u-boot.bin;go 8000000
�cpu2img=u-boot.bin.cpu2
�crc=crc $fileaddr $filesize�sfwr=sf probe 0;tftp b000000 fsoc/spi_boot_fsoc.bin;sf wrimg b000000 0
�bootdelay=3
�baudrate=9600
�ethact=nplite#0
�silent=0
�dhcpen=0
�netmask=255.255.255.0
�imagename=fgt90d.out
�tftport=0
�mac0=08:5b:0e:xx:xx:xx
�sn=FGT90DXXXXXXXXXX
�ver=FortiGate-90D (20:14-02.28.2014)
�bootcmd=flat
�myip=10.10.0.100
�tftpip=10.10.0.10
�gatewayip=10.10.0.101   

Here is the entire bios dump
https://pastebin.pl/view/e641d7a3

Thank you for your help