cmd: fdt: remove CMD_FDT_MAX_DUMP

When printing the device tree we want to get an output that can be used as
input for the device tree compiler. This requires that we do not write
bogus lines like

    pcie@10000000 {
            interrupt-map = * 0x4000127c [0x00000280];

For instance the QEMU virt device has a property interrupt-map with 640
bytes which exceeds CMD_FDT_MAX_DUMP=64.

So lets do away with the artificial limitation to 64 bytes.

As indicated in commit f0a29d43 ("fdt: Limit printed hex in fdt print
and list commands") if a device tree contains binary blobs, it may still
be desirable to limit the output length. Provide environment variable
fdt_max_dump for this purpose.

Fixes: 5d927b42 ("Kconfig: Drop CONFIG_CMD_FDT_MAX_DUMP")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>