ARM: dts: stm32: Duplicate cpu0-opp-table node into stm32mp15-u-boot.dtsi

ARM: dts: stm32: Duplicate cpu0-opp-table node into stm32mp15-u-boot.dtsi

The cpu0-opp-table {} node does not exist in upstream Linux stm32mp151.dtsi
file, in order to enable conversion to OF_UPSTREAM, duplicate the node from
current U-Boot stm32mp151.dtsi into stm32mp15-u-boot.dtsi. This makes STM32
DTs buildable even with OF_UPSTREAM enabled. No functional change, since the
current U-Boot stm32mp151.dtsi already contains the cpu0-opp-table {} node,
stm32mp15-u-boot.dtsi is applied at the end, and does not bring in any new
content.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>