Remove section mismatch - based on ppc aproach.

WARNING: vmlinux.o(.text+0x64834): Section mismatch in reference
from the function __pte_alloc_kernel() to the function .init.text:early_get_page()
The function __pte_alloc_kernel() references
the function __init early_get_page().
This is often because __pte_alloc_kernel lacks a __init
annotation or the annotation of early_get_page is wrong.
Signed-off-by: Michal Simek <monstr@monstr.eu>