Switch Dell 3050 Micro to newer coreboot revision

Specifically, use the same revision that Mate used in patchset 15.

This will ensure that any issues are *not* caused by the coreboot
revision; this is being done, because the old coreboot revision was
from July, but patchset 15 from Mate is based on a September revision
of coreboot.

I've been eliminating as many variables as possible, trying to fix
SeaBIOS payload on this machine, because it hangs in Libreboot, but
not when building from gerrit directly, which means the coreboot
revision may be a factor (since I'm using his patches on an older
revision so upstream might have made some changes since then that
the port relies on).

For this, a new coreboot tree is used, called "dell7", referring to
the fact that Kabylake is Intel's 7th generation.

Signed-off-by: Leah Rowe <leah@libreboot.org>

config/submodule/coreboot/dell7/libgfxinit/module.cfg

@@ -0,0 +1,3 @@
+subrepo="https://review.coreboot.org/libgfxinit.git"
+subrepo_bkup="https://github.com/coreboot/libgfxinit"
+subhash="17cfc92f402493979783585b6581efbd98c0cf07"

config/submodule/coreboot/dell7/libgfxinit/patches/0001-g45-hw-gfx-gma-plls.adb-Make-reference-clock-frequen.patch

@@ -0,0 +1,42 @@
+From ba078864500de99c26b6ea7e3fdcef19bca582a7 Mon Sep 17 00:00:00 2001
+From: Nicholas Chin <nic.c3.14@gmail.com>
+Date: Mon, 20 May 2024 10:10:03 -0600
+Subject: [PATCH 1/1] g45/hw-gfx-gma-plls.adb: Make reference clock frequency
+ configurable
+
+Instead of assuming a 96 MHz reference clock frequency, use the value
+specified by the new INTEL_GMA_DPLL_REF_FREQ Kconfig. This defaults to
+96 MHz to preserve the existing behavior. An example of where this is
+needed is the DPLL_REF_SSCLK input, which will typically be 100 MHz
+to support LVDS spread spectrum clocking.
+
+Signed-off-by: Nicholas Chin <nic.c3.14@gmail.com>
+---
+ common/g45/hw-gfx-gma-plls.adb | 4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+diff --git a/common/g45/hw-gfx-gma-plls.adb b/common/g45/hw-gfx-gma-plls.adb
+index 67242f2..5e970d7 100644
+--- a/common/g45/hw-gfx-gma-plls.adb
++++ b/common/g45/hw-gfx-gma-plls.adb
+@@ -12,6 +12,8 @@
+ -- GNU General Public License for more details.
+ --
+ 
++with CB.Config;
++
+ with HW.Time;
+ with HW.GFX.GMA.Config;
+ with HW.GFX.GMA.Registers;
+@@ -460,7 +462,7 @@ is
+               (Display           => Port_Cfg.Display,
+                Target_Dotclock   => Target_Clock,
+                -- should be, but doesn't has to be always the same:
+-               Reference_Clock   => 96_000_000,
++               Reference_Clock   => CB.Config.INTEL_GMA_DPLL_REF_FREQ,
+                Best_Clock        => Clk,
+                Valid             => Success);
+          else
+-- 
+2.39.2
+