rdp: fix return value test of csp_rdp_receive_data
rdp: fix return value test of csp_rdp_receive_data

Psykar/kubos,satlab/libcsp,pacheco017/libcsp,marshall/libcsp,pacheco017/libcsp,libcsp/libcsp,GomSpace/libcsp,pacheco017/libcsp,kubostech/KubOS,satlab/libcsp,satlab/libcsp,kubostech/KubOS,Psykar/kubos,Psykar/kubos,marshall/libcsp,GomSpace/libcsp,Psykar/kubos,GomSpace/libcsp,pacheco017/libcsp,libcsp/libcsp,Psykar/kubos,Psykar/kubos,marshall/libcsp,Psykar/kubos