u-boot mainline AM4 Mini board support

U-Boot SPL 2021.10-rc5-00001-g3cfe618ccec9 (Sep 27 2021 - 23:47:10 +0200)
Trying to boot from MMC1


U-Boot 2021.10-rc5-00001-g3cfe618ccec9 (Sep 27 2021 - 23:47:10 +0200)

CPU  : AM437X-GP rev 1.2
Model: TI AM437x GP EVM MINI
DRAM:  1 GiB
MMC:   OMAP SD/MMC: 0
Loading Environment from FAT... Unable to read "uboot.env" from mmc0:1... Hit any key to stop autoboot:  0
=> version
U-Boot 2021.10-rc5-00001-g3cfe618ccec9 (Sep 27 2021 - 23:47:10 +0200)

arm-linux-gnueabi-gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
GNU ld (GNU Binutils for Ubuntu) 2.34
=> i2c dev 0
Setting bus to 0
=> i2c speed
Current bus speed=100000
=> reset
resetting ...

U-Boot SPL 2021.10-rc5-00001-g3cfe618ccec9 (Sep 27 2021 - 23:47:10 +0200)
Trying to boot from MMC1


U-Boot 2021.10-rc5-00001-g3cfe618ccec9 (Sep 27 2021 - 23:47:10 +0200)

CPU  : AM437X-GP rev 1.2
Model: TI AM437x GP EVM MINI
DRAM:  1 GiB
MMC:   OMAP SD/MMC: 0
Loading Environment from FAT... Unable to read "uboot.env" from mmc0:1... Hit any key to stop autoboot:  0
=>