realtek: Convert incorrect v5.10 patches

OpenWRT's developer guide prefers having actual patches so they an be
sent upstream more easily.

However, in this case, Adding proper fields also allows for `git am` to
properly function. Some of these patches are quite old, and lack much
traceable history.

This commit tries to rectify that, by digging in the history to find
where and how it was first added.

It is by no means perfect and also shows some patches that should have
been long gone.

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>

target/linux/realtek/patches-5.10/301-gpio-add-rtl8231-driver.patch

@@ -1,3 +1,28 @@
+From 2b88563ee5aafd9571d965b7f2093a0f58d98a31 Mon Sep 17 00:00:00 2001
+From: John Crispin <john@phrozen.org>
+Date: Thu, 26 Nov 2020 12:02:21 +0100
+Subject: [PATCH] realtek: update the tree to the latest refactored version
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+* rename the target to realtek
+* add refactored DSA driver
+* add latest gpio driver
+* lots of arch cleanups
+* new irq driver
+* additional boards
+
+Submitted-by: Bert Vermeulen <bert@biot.com>
+Submitted-by: Birger Koblitz <mail@birger-koblitz.de>
+Submitted-by: Sander Vanheule <sander@svanheule.net>
+Submitted-by: Bjørn Mork <bjorn@mork.no>
+Submitted-by: John Crispin <john@phrozen.org>
+---
+ drivers/gpio/Kconfig                          |    6 ++++++
+ drivers/gpio/Makefile                         |    1 +
+ 2 files changed, 7 insertions(+)
+
 --- a/drivers/gpio/Kconfig
 +++ b/drivers/gpio/Kconfig
 @@ -508,6 +508,12 @@ config GPIO_REG