x86: unify mmap_{32|64}.c

mmap_is_ia32 always true for X86_32, or while emulating IA32 on X86_64

Randomization not supported on X86_32 in legacy layout.  Both layouts allow
randomization on X86_64.

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>