mvebu: eDPU: disable SCSI support

eDPU does not use SCSI nor it has SATA exposed, and commit
arm: mvebu: a3720: Set BOOT_TARGET_DEVICES list to enabled peripherals
now allows compiling U-boot wihout all of the BOOT_TARGET_DEVICES since
not all boards have all of the listed peripherals exposed.

So, disable SCSI support in defconfig for eDPU.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>