Update kernel support list (more recent version than 5.4 may fail though)

.travis.yml

@@ -85,9 +85,8 @@ matrix:
           sources:
             - ubuntu-toolchain-r-test
 
-    # Stable versions
+    - name: "Kernel 5.4.y LTS"
-    - name: "Kernel 5.3.y STABLE"
+      env: KERNEL_BRANCH="linux-5.4.y" GCC_VER="gcc-8"
-      env: KERNEL_BRANCH="linux-5.3.y" GCC_VER="gcc-8"
       addons:
         apt:
           packages:
@@ -96,8 +95,19 @@ matrix:
           sources:
             - ubuntu-toolchain-r-test
 
-    - name: "Kernel 5.4.y STABLE"
+    # Stable versions
-      env: KERNEL_BRANCH="linux-5.4.y" GCC_VER="gcc-8"
+    - name: "Kernel 5.7.y STABLE"
+      env: KERNEL_BRANCH="linux-5.7.y" GCC_VER="gcc-8"
+      addons:
+        apt:
+          packages:
+            - libelf-dev
+            - gcc-8
+          sources:
+            - ubuntu-toolchain-r-test
+
+    - name: "Kernel 5.8.y STABLE"
+      env: KERNEL_BRANCH="linux-5.8.y" GCC_VER="gcc-8"
       addons:
         apt:
           packages: