dts: arm: stm32h7Ax/h7Bx have octospi peripĥerals

Add the octospi nodes to the stm32h7A3 and
and h7B0/h7B3 devices.
Note that RM0455 gives a size of 1kB.
The definition of the octospi clock source for both intances
is given by the DTS node. The selected value for
the alternate clock control is the PLL1_Q.

Signed-off-by: Francois Ramu <francois.ramu@st.com>