tools/bluemoon: Fix compilation error/warning
tools/bluemoon: Fix compilation error/warning

This patch fixes the following error/warning:

  CC tools/bluemoon.o
tools/bluemoon.c: In function ‘analyze_firmware’:
tools/bluemoon.c:813:10: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
  if (len != le32_to_cpu(css->size) * 4) {
          ^
cc1: all warnings being treated as errors

pstglia/external-bluetooth-bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez,pkarasev3/bluez,mapfau/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,silent-snowman/bluez,mapfau/bluez,silent-snowman/bluez,ComputeCycles/bluez,pkarasev3/bluez,pkarasev3/bluez,silent-snowman/bluez,ComputeCycles/bluez,ComputeCycles/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez