x86, core: remove CONFIG_FORCED_INLINING

Other than the defconfigs, remove the entry in compiler-gcc4.h,
Kconfig.debug and feature-removal-schedule.txt.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>