grub/xhci: Remove unused patch

I was importing a patch for the z790 boards, but
Libreboot doesn't support this board yet, and the
patch was a hack that may affect other boards.

When I do later merge that board, and I find that the
hack is needed, I'll simply make another grub tree
within lbmk.

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

config/grub/xhci/patches/0023-xhci-workaround-z790-non-root-hub-speed-detection.patch

@@ -1,28 +0,0 @@
-From 70731c46da05311edb639ce1349bb6dd3279031e Mon Sep 17 00:00:00 2001
-From: Sven Anderson <sven@anderson.de>
-Date: Mon, 13 Jan 2025 19:55:15 +0100
-Subject: [PATCH 23/26] xhci: workaround z790 non-root-hub speed detection
-
----
- grub-core/bus/usb/xhci.c | 5 +++++
- 1 file changed, 5 insertions(+)
-
-diff --git a/grub-core/bus/usb/xhci.c b/grub-core/bus/usb/xhci.c
-index dc89b9619..d13a7c39d 100644
---- a/grub-core/bus/usb/xhci.c
-+++ b/grub-core/bus/usb/xhci.c
-@@ -2285,6 +2285,11 @@ grub_xhci_detect_dev (grub_usb_controller_t dev, int port, int *changed)
-   if (!(portsc & GRUB_XHCI_PORTSC_CCS))
-     return GRUB_USB_SPEED_NONE;
- 
-+  if (port == 4 || port == 12 && speed < XHCI_USB_HIGHSPEED) { // inital hub speed detection on Z790 is too low
-+    grub_dprintf("xhci", "%s: setting internal hub speed to high\n", __func__);
-+    return GRUB_USB_SPEED_HIGH;
-+  }
-+
-   for (grub_uint8_t i = 0; i < 16 && x->psids[port].psids[i].id > 0; i++)
-     {
-       if (x->psids[port].psids[i].id == speed)
--- 
-2.39.5
-