dm: spi: Read default speed and mode values from DT

dm: spi: Read default speed and mode values from DT

In case of DT boot, don't read default speed and mode for SPI from
CONFIG_*, instead read from DT node. This will make sure that boards
with multiple SPI/QSPI controllers can be probed at different
bus frequencies and SPI modes.

Signed-off-by: Vignesh R <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Reviewed-by: Mugunthan V N <[email protected]>
Reviewed-by: Jagan Teki <[email protected]>