[RFC PATCH] gcc-9: workaround array bounds warning on boot_params cleaning

[Fihlman Emil]

It should also be possibly to simply cast to u64 and then to u8 * unless
the compiler overzealously tracks out of bound accesses even when
6.3.2.3 #5-6 explicitly allows pointer-integer-pointer conversions like
this and removes previous guarantees. Ie.

memset((u8 *)((u64)(&(boot_params->ext_ramdisk_image))), 0, size)

I apologise for not having the in-reply-to header.

Emil Fihlman