x86: cpu: i386: cpu: only set pci_ram_top if CONFIG_IS_ENABLED(PCI)

This avoids an error when ifdef CONFIG_PCI is changed to
if CONFIG_IS_ENABLED(PCI)

Signed-off-by: Troy Kisky <troykiskyboundary@gmail.com>
[Rebased on top of u-boot/master]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2 files changed