Make code better readable by replacing `if (rsp->ccode > 0)`
and 'if (rsp->ccode != 0)' with just `if (rsp->ccode)` as
rsp->ccode is anyway an unsigned byte and can't be negative.
Also replace 'if (rsp->ccode == 0)' with 'if (!rsp->ccode)'.
All these changes make lines shorter and easier to read as
a non-zero ccode is an indication of some failure, and so !ccode
naturally reads as 'no error'.
Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>