arm64: dts: ti: k3-am62*: remove SoC dtsi from common dtsi

arm64: dts: ti: k3-am62*: remove SoC dtsi from common dtsi

The k3-am62x-sk-common dtsi represents the common hardware used across
am62x EVMs which can be configured with various DDR sizes or none (with
DDR integrated in the package) based on the specific am62x SoC used.

Therefore this patch moves the memory node and the SoC specific k3-am625
dtsi out of sk-common and into the board dts files. No functional change
is intended from this patch. The device-tree inheritance is changed as
follows:

Before:

               k3-am62
                 ^
               k3-am625
                 ^
         k3-am62x-sk-common
                 ^
  am62x EVMs (k3-am625-sk, k3-am62-lp-sk)

After:

        k3-am62
          ^
        k3-am625    k3-am62x-sk-common
          ^              ^
  am62x EVMs (k3-am625-sk, k3-am62-lp-sk)

Signed-off-by: Anshul Dalal <anshuld@ti.com>
Reviewed-by: Bryan Brattlof <bb@ti.com>
Link: https://patch.msgid.link/20250814134531.2743874-2-anshuld@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>