x86, microcode, AMD: Fix early ucode loading

The original idea to use the microcode cache for the APs doesn't pan out
because we do memory allocation there very early and with IRQs disabled
and we don't want to involve GFP_ATOMIC allocations. Not if it can be
helped.

Thus, extend the caching of the BSP patch approach to the APs and
iterate over the ucode in the initrd instead of using the cache. We
still save the relevant patches to it but later, right before we
jettison the initrd.

While at it, fix early ucode loading on 32-bit too.

Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>