xilinx: Disable CONFIG_EFI_LOADER_BOUNCE_BUFFER for ZynqMP/Versal

Both SOCs shouldn't have any problem with 64bit dma accesses. Also with PIE
enabled when u-boot is placed above 4GB without any memory mapped below 4GB
address space efi_memory_init() call is failing due to missing memory node.

For this two reason disable this option for ZynqMP and Versal.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>