Prefix internal functions and structs with modbus_.
Use unit_id consistently instead of node_addr.
Fix mbm_ remainder and rename to mbc_.
Rename struct modbus_frame to modbus_adu since
ADU is closer to what the structure represents.
Let the compiler/linker do the job and
remove ifdef around mbc_validate_fc03fp_response().
Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>
