configs/beaglev: update U-Boot to enable OF_SEPARATE

configs/beaglev: update U-Boot to enable OF_SEPARATE

Update commit ID of U-Boot to latest commit in starfive-tech repo [1]
which enables OF_SEPARATE [2].

[1] https://github.com/starfive-tech/u-boot/tree/Fedora_VIC_7100_2021.04
[2] https://github.com/starfive-tech/u-boot/commit/64ead5b83959da8eb87b6963843addf5942e6ed4

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Drew Fustini <drew@beagleboard.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>