imx: hab: fix size of IVT+CSF blob tacked on to u-boot.itb

imx: hab: fix size of IVT+CSF blob tacked on to u-boot.itb

Loading flash.bin using uuu fails when flash.bin does not have the
right size.

When flash.bin is loaded from some storage medium (sd card/emmc), SPL
just loads some random garbage bytes from beyond what has been
populated when flash.bin was written, but when loaded via uuu, SPL
hangs waiting for the host to send the expected number of bytes. Which
is (size of FIT image aligned to 0x1000)+CONFIG_CSF_SIZE. The
alignment to 0x1000 is already done and is necessary in all cases
because that's the exact expected location of the 32 byte IVT
header. But the IVT+CSF blob tacked onto the end must be a total of
CONFIG_CSF_SIZE.

This is exactly the same fix as 89f19f45d650, except that this time
around I don't know how to cleanly get CONFIG_CSF_SIZE.

Fixes: bc6beae7c55f (binman: Add nxp_imx8mcst etype for i.MX8M flash.bin signing)
Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
Tested-by: Heiko Schocher <hs@denx.de>