gen5200, gen83xx, gen83x, mpc55xxevb, psim, qoriq, t32mppc, tqm8xx, virtex: Simplify bsp_specs
These BSPs all use shared/startup/linkcmds.base and thus needed to be modified at the same time. Variations in the arguments were reflected into the BSP specific portions of the linkcmds.
Updates #3520.