arm64: dts: ti: iot2050: Prepare for adding 2nd-generation boards

The current IOT2050 devices are Product Generation 1 (PG1), using SR1.0
AM65x silicon. Upcoming PG2 devices will use SR2.x SoCs and will
therefore need separate device trees. Prepare for that by factoring out
common bits that will be shared across both generations.

At this chance, drop a link to the product homepage to in the top-level
dts files. Also fix a typo in my email address in some headers.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/31fece05f9728a852c0632985c4fa537cced4ece.1632657917.git.jan.kiszka@web.de