Network backend: Add network_get_buffer() backend function
Network backend: Add network_get_buffer() backend function

For now, this function is only available on non-cyclic TX buffers.
It is better than the network_write() function, as the data is
transferred to the socket without being copied.

Signed-off-by: Paul Cercueil <73d292422978d45c9eeef455bb1b24a0db453722@analog.com>

Sunderfield/libiio,gburca/libiio,analogdevicesinc/libiio,sensarliar/libiio,analogdevicesinc/libiio,sensarliar/libiio,sensarliar/libiio,gburca/libiio,gburca/libiio,analogdevicesinc/libiio,Sunderfield/libiio,Sunderfield/libiio,analogdevicesinc/libiio