boards: arm: stm32u5 disco kit target board has octo SPI instance

This commit enables the octo SPI peripheral to the flash-nor
on the target board b_u585i_iot02a from STMicroelectronics.
Note that JESD16 requires 9 dwords for the sdfp table.
The configuration is for OctoSPI bus through IO manager.
The NOR octoflash is MX25LM51245 or compatible.

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