util/bincfg: Add DDR4 SPD spec

Additionally provide a simple script for decoding spd hex files using bincfg.

BUG=b:148561711
TEST=Decoded spd files in zork
BRANCH=None

Change-Id: Ic62868d59e075fd6816d7be55cc935e3e3f82499
Signed-off-by: Rob Barnes <robbarnes@google.com>
Reviewed-on: https://chromium-review.googlesource.com/2067697
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39621
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michael Niewöhner

util/scripts/description.md

@@ -3,6 +3,8 @@ __scripts__
               line `Bash`
   * _cross-repo-cherrypick_ - Pull in patches from another tree from a
                               gerrit repository. `Shell`
+  * _decode_spd.sh_ - Decodes Serial Presence Detect (SPD) files into
+                      various human readable formats.
   * _dts-to-fmd.sh_ -Converts a depthcharge fmap.dts into an fmaptool
                      compatible .fmd format `Bash`
   * _find-unused-kconfig-symbols.sh_ - Points out Kconfig variables