x86: Remove CPU_INTEL_SOCKET_RPGA989

This Kconfig option name indicates it has something to do with cpu
socket, however it is actually not the case. Remove it and move
options inside it to NORTHBRIDGE_INTEL_IVYBRIDGE.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>