MIPS: mm: init: Add free_init_pages() callback for EVA

A core in EVA mode can have any possible segment mapping, so the
default free_initmem_default() function may not always work as expected.
Therefore, add a callback that platforms can use to free up the init section.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

diff --cc arch/mips/include/asm/bootinfo.h
Simple merge

diff --cc arch/mips/mm/init.c
Simple merge