cpu/x86/16bit: rename _start -> _start16bit

In order to avoid collisions with other _start symbols while
grepping and future ones be explicit about which _start this
one is: the 16-bit one only used by the reset vector in the

Change-Id: I6d7580596c0e6602a87fb158633ce9d45910cec2
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13880
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)
3 files changed