boards: arm: stm32u585 and stm32l562 disco octoflash in SPI mode

The four-byte-opcodes property of the octoFlash node must be set to
use a 4-byte opcode (SPI_NOR_CMD_PP_4B) in the case of OSPI_SPI_MODE.
Else the write instruction is wrong and the operation fails
in this transfer data mode

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