uboot-imx

MIPS: define __init_end in u-boot.lds

The generic board code uses the __init_end symbol to calculate
monitor_flash_len. Define said symbol for MIPS, equivalent to
__image_copy_end which is used for the same purpose in
arch/mips/lib/board.c.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>