certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID

Align with the new macros and add appropriate include files.

Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>