Update build workflow to trigger on main branch

Author: kendryte747

.github/workflows/build.yml

@@ -3,7 +3,7 @@ name: Build Prebuilt u-boot
 on:
   push:
     branches:
-      - canmv_k230
+      - main
       - action
 
 jobs:
@@ -104,7 +104,7 @@ jobs:
             [k230d_canmv_junroc_ai_cam_defconfig]="k230d_canmv_junroc_ai_cam"
             [k230d_canmv_labplus_ai_camera_defconfig]="k230d_labplus_ai_camera"
             [k230d_canmv_labplus_ai_camera_v2_defconfig]="k230d_labplus_ai_camera_v2"
-            [k230d_canmv_lushanpi_lite_defconfig]="k230d_lushanpi_lite"
+            [k230d_canmv_lushanpi_lite_defconfig]="k230d_canmv_lushanpi_lite"
           )
 
           echo "Defconfigs: ${!defconfig_to_board[@]}"