kexec: ensure kexec_status() return bit value of 0 or 1

When checking kexec_flags bit corresponding to the
requested image, ensure that 0 or 1 is returned.

Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/common/kexec.c

@@ -1182,7 +1182,7 @@ static int kexec_status(XEN_GUEST_HANDLE_PARAM(void) uarg)
     if ( kexec_load_get_bits(status.type, &base, &bit) )
         return -EINVAL;
 
-    return test_bit(bit, &kexec_flags);
+    return !!test_bit(bit, &kexec_flags);
 }
 
 static int do_kexec_op_internal(unsigned long op,