x86/boot: Use CC_SET()/CC_OUT() instead of open coding it

Remove open-coded uses of set instructions with CC_SET()/CC_OUT().

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20180629142844.15200-1-ubizjak@gmail.com