Only one binary blob is needed for Remote Management Unit (RMU) within Intel Quark SoC. Not like FSP, U-Boot does not call into the binary. The binary is needed by the Quark SoC itself.
You can get the binary blob from Quark Board Support Package from Intel website:
Rename the file and put it to the board directory by:
$ cp RMU.bin board/intel/galileo/rmu.bin
Now you can build U-Boot and obtain u-boot.rom:
$ make galileo_defconfig $ make all