x86/kaslr: Have process_mem_region() return a boolean

Fix the following coccicheck warning:

  ./arch/x86/boot/compressed/kaslr.c:671:10-11:WARNING:return of 0/1
  in function 'process_mem_region' with return type bool

Generated by: scripts/coccinelle/misc/boolreturn.cocci

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210824070515.61065-1-deng.changcheng@zte.com.cn