fdt: Fix uncompress_blob() for U-Boot proper

When U-Boot proper is compiled with CONFIG_MULTI_DTB_FIT and tries
to call uncompress_blob(), it fails with -ENOTSUPP. This is because
the full implementation of this function which includes compression
is available only in SPL. In U-Boot proper or if the compression is
not enabled, the blob is not compressed and thus can be passed to
locate_dtb_in_fit() in fdtdec_setup() without any changes. Pass the
blob without any changes if compression is not enabled instead of
failing.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>