Correct FPGA cache key command for RTL directory (#1591)

.github/workflows/fpga.yml

@@ -63,7 +63,7 @@ jobs:
           else
             RTL_VERSION="latest"
           fi
-          echo "rtl_cache_key=$(git rev-parse HEAD:hw/fpga/src)-$(git hash-object hw/fpga/fpga_configuration.tcl)-$(cd hw/${RTL_VERSION}/rtl && git rev-parse HEAD:)-${{ inputs.fpga-itrng }}-${{ env.CACHE_BUSTER }}" >> $GITHUB_OUTPUT
+          echo "rtl_cache_key=$(git rev-parse HEAD:hw/fpga/src)-$(git hash-object hw/fpga/fpga_configuration.tcl)-$(cd hw/${RTL_VERSION}/rtl && git rev-parse HEAD)-${{ inputs.fpga-itrng }}-${{ env.CACHE_BUSTER }}" >> $GITHUB_OUTPUT
 
           echo "kmod_cache_key=fpga-kernel-modules-$(git rev-parse HEAD:hw/fpga/io_module)-$(git rev-parse HEAD:hw/fpga/rom_backdoor)-${{ env.CACHE_BUSTER }}" >> $GITHUB_OUTPUT