clearfog: Enable up to 64kB transfers over spidev

These SPI transfer limits affect not only regular read()/write() calls,
but also the more generic ioctl interface.

Change-Id: Ibdedd266becb3c5533af7fe1bdb061637c0eadd8
diff --git a/board/czechlight/clearfog/boot.scr.txt b/board/czechlight/clearfog/boot.scr.txt
index 2777ba8..bb48d89 100644
--- a/board/czechlight/clearfog/boot.scr.txt
+++ b/board/czechlight/clearfog/boot.scr.txt
@@ -1,4 +1,5 @@
 setenv bootargs root=/dev/mmcblk0p${rauc_part} rauc.slot=${rauc_slot} czechlight=${czechlight} systemd.machine_id=${machineid} panic=10 oops=panic
+setenv bootargs ${bootargs} spidev.bufsiz=65535
 if load mmc 0:${rauc_part} ${fdt_addr_r} /boot/${czechlight}-clearfog.dtb; then
   echo "DTS: ${czechlight}-clearfog"
 else