x86/e820: Use proper booleans instead of 0/1

This fixes the following coccinelle warning:
./arch/x86/kernel/e820.c:89:9-10: WARNING: return of 0/1 in function '_e820__mapped_any' with return type bool

Return type bool instead of 0/1.

Signed-off-by: Yi Wang <wang.yi59@zte.com.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1563158829-44373-1-git-send-email-wang.yi59@zte.com.cn