Update Readme

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>

README.md

@@ -36,7 +36,7 @@ cd -
 
 ```
 cd u-boot
-ARCH=arm CROSS_COMPILE=aarch64-linux-gnu- make rpi_4_defconfig
+ARCH=arm CROSS_COMPILE=aarch64-linux-gnu- make rpi_4_acpi_defconfig
 ARCH=arm CROSS_COMPILE=aarch64-linux-gnu- make -j$(nproc)
 cd -
 ```
@@ -71,14 +71,6 @@ Now plug out the SD card and put it into the raspberry PI 4 B
 
 ## Workflow
 
-This project uses git subtrees. The Idea is that you only use this repository to make changes and leave the u-boot-acpi repo alone.
-
-If you do changes inside of the u-boot repository you can commit them like usual. In order to push a commit that makes changes inside the u-boot directory do the following command:
-```
-git subtree push --prefix u-boot [remote that points to u-boot-acpi repo] master
-```
-This will automatically push the changes to the u-boot-acpi repository as well as keep the change in this repository.
-
 ## Testing in QEMU:
 
 Starting with QEMU 9.0 you can run the RPI 4 in qemu: