configure: add hint of libfdt to DTC dependency not found message

Most distros package it as libfdt, and mentioning libfdt here makes it
much easier to find the package you're missing.

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/configure b/configure
index 88133a1..f58fa84 100755
--- a/configure
+++ b/configure
@@ -2662,8 +2662,8 @@
     fdt_libs="-L\$(BUILD_DIR)/dtc/libfdt $fdt_libs"
   elif test "$fdt" = "yes" ; then
     # have neither and want - prompt for system/submodule install
-    error_exit "DTC not present. Your options:" \
-        "  (1) Preferred: Install the DTC devel package" \
+    error_exit "DTC (libfdt) not present. Your options:" \
+        "  (1) Preferred: Install the DTC (libfdt) devel package" \
         "  (2) Fetch the DTC submodule, using:" \
         "      git submodule update --init dtc"
   else