bluez5_utils: fix big endian build

This patch has been accepted upstream and requires no changes to apply
to 5.37.

Fixes:

  http://autobuild.buildroot.org/results/2bf4e5ea9b67b80ba38bfeaf71b747a92be09011/



Signed-off-by: John Keeping <john@metanate.com>
[Thomas:
 - add reference to upstream commit
 - add John's SoB to the patch itself
 - add reference to autobuilder failure.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>