Normalize global variables exported by vmlinux.lds to conform usage
guidelines from include/asm-generic/sections.h.

Use _text to mark the start of the kernel image including the head text,
and _stext to mark the start of the .text section.
Signed-off-by: NJiang Liu <jiang.liu@huawei.com>
Acked-by: NHans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>