configs: sama5d27_som1_ek: qspi: use common memory layout

Use the qspi memory layout defined in at91-sama5_common - it aligns
with the 8 Mbyte flash (sst26vf064b-104i/sn) available in sama5d27_som1_ek.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>