powerpc/mpc85xx: socrates: rework build process

U-Boot build process for socrates board produces final U-Boot binary in
file u-boot-socrates.bin (by binman) And as a bonus it produces two
unusable broken binaries u-boot-dtb.bin and u-boot.bin (by Makefile).

Clean this up, so final U-Boot binary is in u-boot-dtb.bin

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Heiko Schocher <hs@denx.de>
3 files changed