make show_boot_progress () weak.

common/cmd_bootm.c

common/cmd_doc.c

common/cmd_ide.c

common/cmd_nand.c

common/cmd_net.c

common/env_common.c

common/main.c

drivers/nand_legacy/nand_legacy.c

include/common.h

lib_arm/armlinux.c

lib_avr32/avr32_linux.c

lib_blackfin/bf533_linux.c

lib_blackfin/post.c

lib_m68k/m68k_linux.c

lib_microblaze/microblaze_linux.c

lib_mips/mips_linux.c

lib_ppc/board.c

net/eth.c

post/post.c