Revert "ARM: dts: k3-am642-sk-u-boot: add PMIC node"

This reverts commit 28a4c311.

This node should be in the board DT file and should come from upstream.
Moreover, this PMIC is no present on all variants of am642-sk
and will need a separate board DT file.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Nishanth Menon <nm@ti.com>
Tested-by: Nishanth Menon <nm@ti.com> #SK-AM64B