Remove address-of operator ('&') when assigning `init_fn`
function pointer in `DEVICE_DT_INST_DEFINE` macro.
This change aims to maintain consistency among the drivers in
`drivers/spi`, ensuring that all function pointer assignments
follow the same pattern.
Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>
This change marks each instance of the 'spi_driver_api' as 'static const'.
The rationale is that 'spi_driver_api' is used for declaring internal
module interfaces and is not intended to be modified at runtime.
By using 'static const', we ensure immutability, leading to usage of only
.rodata and a reduction in the .data area.
Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>