lib: Fix compilation error in C++ due to inline function
lib: Fix compilation error in C++ due to inline function

This adds explicit typecasts to an inline function to make it C++
compatible. What follows is a sample error message from g++ when
compiling without this patch.

/usr/include/bluetooth/bluetooth.h:
  In function 'void bswap_128(const void*, void*)':
/usr/include/bluetooth/bluetooth.h:348:21:
  error: invalid conversion from 'const void*' to 'const uint8_t*
         {aka const unsigned char*}' [-fpermissive]
  const uint8_t *s = src;

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