powerpc: mpc85xx: Drop u-boot-with-spl.bin on selected boards

For SoCs with PBL, u-boot-with-spl-pbl.bin is the final image for
SPL boot. Drop unused u-boot-with-spl.bin.

Signed-off-by: York Sun <york.sun@nxp.com>
CC: Ashish Kumar <ashish.kumar@nxp.com>
CC: Ruchika Gupta <ruchika.gupta@nxp.com>
CC: Priyanka Jain <priyanka.jain@nxp.com>
CC: Shengzhou Liu <Shengzhou.Liu@nxp.com>