configs: sama5d27_som1_ek: Add default config to read ENV from QSPI

In the initial SPI flash setup, the default bus mode being used was 3,
which is incorrect, causing a CRC error when the ENV was being read from
QSPI. Setting the default bus mode to 0 which is the correct mode.

Signed-off-by: Swapna Gurumani <swapna.gurumani@microchip.com>