ARM: dts: bcm-mobile: Split out nodes used by both BCM21664 and BCM23550

ARM: dts: bcm-mobile: Split out nodes used by both BCM21664 and BCM23550

The BCM21664 is nearly identical in terms of register layout to the
BCM23550. Move the shared nodes into a new file, bcm2166x-common.dtsi,
and make both bcm21664.dtsi and bcm23550.dtsi include it. This new
common file is based on the former bcm23550.dtsi file, and inherits
its licensing.

Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
Link: https://lore.kernel.org/r/20240729-bcm21664-common-v2-2-ebc21a89bf63@gmail.com
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>