arm: rockchip: Add RK3576 arch core support

The Rockchip RK3588 is a ARM-based SoC with quad-core Cortex-A72
and quad-core Cortex-A53 including 6TOPS NPU, Mali-G52 MC3, HDMI Out,
DP, eDP, MIPI DSI, MIPI CSI2, LPDDR4/4X/5, eMMC5.1, SD3.0/MMC4.5, UFS,
USB OTG 3.0, Type-C, USB 2.0, PCIe 2.1, SATA 3, Ethernet, SDIO3.0, I2C,
UART, SPI, GPIO and PWM.

Add arch core support for it.

Signed-off-by: Xuhui Lin <xuhui.lin@rock-chips.com>
[adapted for mainline u-boot]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>