fix(risc): check for device tree

Author: elge@alpha15

bare-metal/elastic-metal/reference-content/elastic-metal-rv1-guidelines.mdx

@@ -70,6 +70,13 @@ Linux kernel.
 4. Build the Linux kernel.
     ```bash
     cd linux/
+
+    # Make sure the device required device tree is available in the default branch
+    ls -lhF arch/riscv/boot/dts/thead/th1520-lichee-cluster-4a-16g.dts
+    # Otherwise switch to another branch that has it
+    #git branch -a
+    #git switch ...
+
     make revyos_defconfig
     # This can take several hours.
     make -j4
@@ -86,12 +93,6 @@ Linux kernel.
    ```bash
    cd em-rv1/fit/
 
-   # Fix path to board device tree
-   ls -lF ../../linux/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a-16g.dts
-   vi em-rv1-c4m16s128-a.dts
-
-   #include "th1520-lichee-pi-4a-16g.dts"
-
    # Build the device tree
    cpp \
     -nostdinc \