drivers: flash: stm32 ospi driver defines the dlyb-bypassed property

The delayblock is bypassed when the <dlyb-bypass> property is true.
DT_NODE_HAS_PROP tests whether the property is defined at all,
not whether a boolean property is true or false.
To get a boolean property’s truth value,
use DT_PROP(node_id, prop) instead.

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