uboot-mvebu: add patch to enable setexpr for clearfog boards

uboot-mvebu: add patch to enable setexpr for clearfog boards

Option CMD_SETEXPR is already default in U-boot [1], since this was
disabled since initial version for this board, there is send this
	patch to U-boot mailing list to enable it.

It is required to use in OpenWrt bootscript for these boards [2].

[1] https://source.denx.de/u-boot/u-boot/-/blob/e95afa56753cebcd20a5114b6d121f281b789006/cmd/Kconfig#L1504

[2] https://github.com/openwrt/openwrt/blob/852126680e21edc71c0c66561ae5a6d7479dcc67/target/linux/mvebu/image/clearfog.bootscript#L7

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>