N310 set_rx_gain nonfunctional behaviour

[asut6330]

Issue Description

When setting rx_gain_profile=manual and setting the gain of the various front end components (amp/dsa/rfic), there is buggy behavior exhibited. Firstly, the rfic gain has an inversion, for instance,
usrp->set_rx_gain(0, "rfic", 0);
printf("Gain rfic: %f dB\n", usrp->get_rx_gain("rfic", 0));
will print,
"Gain rfic: 30.000000 dB"

The set function seems to actually perform 30-gain.

Additionally, setting the "dsa" has no effect despite the step attenuator clearly being present in the frontend of the N310 device, as shown in the schematics.
usrp->set_rx_gain(0, "dsa", 0);

Can this functionality be confirmed in earlier versions of UHD?

Setup Details

[INFO] [UHD] linux; GNU C++ version 9.4.0; Boost_107100; UHD_4.3.0.0-15-g5333d3d1

-- UHD Device 0

Device Address:
serial: 322C655
addr: 192.168.20.2
claimed: False
fpga: HG
mgmt_addr: 192.168.1.106
mgmt_addr: 192.168.20.2
name: ni-n3xx-322C655
product: n310
type: n3xx

Steps to reproduce the problem

` printf("Gain range start rfic: %f dB\n", usrp->get_rx_gain_range("rfic", 0).start());
printf("Gain range end rfic: %f dB\n", usrp->get_rx_gain_range("rfic", 0).stop());
usrp->set_rx_gain(0, "rfic", 0);
printf("Gain rfic: %f dB\n", usrp->get_rx_gain("rfic", 0));

printf("Gain range start dsa: %f dB\n", usrp->get_rx_gain_range("dsa", 0).start());
printf("Gain range end dsa: %f dB\n", usrp->get_rx_gain_range("dsa", 0).stop());
usrp->set_rx_gain(-15, "dsa", 0);
printf("Gain dsa: %f dB\n", usrp->get_rx_gain("dsa", 0));

printf("Gain range start amp: %f dB\n", usrp->get_rx_gain_range("amp", 0).start());
printf("Gain range end amp: %f dB\n", usrp->get_rx_gain_range("amp", 0).stop());
usrp->set_rx_gain(10, "amp", 0);
printf("Gain amp: %f dB\n", usrp->get_rx_gain("amp", 0));`