x86: unify mm_segment_t definition

This patch moves the mm_segment_t structure definition to processor.h
This makes mmsegment.h file useless, and it is deleted.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>