x86/microcode/AMD: Rip out static buffers

Load straight from the containers (initrd or builtin, for example).
There's no need to cache the patch per node.

This even simplifies the code a bit with the opportunity for more
cleanups later.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: John Allen <john.allen@amd.com>
Link: https://lore.kernel.org/r/20230720202813.3269888-1-john.allen@amd.com