mmap-alloc: unfold qemu_ram_mmap()

mmap-alloc: unfold qemu_ram_mmap()

Unfold parts of qemu_ram_mmap() for the sake of understanding, moving
declarations to the top, and keeping architecture-specifics in the
ifdef-else blocks.  No changes in the function behaviour.

Give ptr and ptr1 meaningful names:
  ptr  -> guardptr : pointer to the PROT_NONE guard region
  ptr1 -> ptr      : pointer to the mapped memory returned to caller

Signed-off-by: Murilo Opsfelder Araujo <[email protected]>
Reviewed-by: Greg Kurz <[email protected]>
Signed-off-by: David Gibson <[email protected]>