[U-Boot] Some question about uboot

Dear all: While porting uboot, I find there are too many things I don't need at all, like net, i2c etc. How could I remove them from my uboot binary to minimize the size of uboot, my flash limitation is 6k? I try to edit Makefile to remove them by marking some library setting, but it compile error after I doing so. Is there any easier way to meet my requirement? Appreciate your help, miloody