rockchip: dts: Sync ROC-RK3399-PC changes from Linux

Sync the ROC-RK3399-PC device tree changes from Linux
with below commit details:

commit <c36308abe4110e4db362d5e2ae3797834a7b1192> ("arm64: dts:
rockchip: Enable MTD Flash on rk3399-roc-pc")

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>