moby: actually, just disable the debug uart pull resistor

hosts/modules/hal/pine64-pinephone-pro/rk3399-pinephone-pro-sound.dtso

@@ -289,10 +289,11 @@
                         // unfortunately it's not designed to handle below-ground signals.
                         // long-term fix is to mix a DC offset into the amp output.
                         // until then, pull RX to *ground* instead of supply, so that it's less affected by (apparent) shorting with the HPOL channel.
+                        // or even just leave it without any pull resistor -- so far that seems to be pretty stable?
                         // note that this only fixes the spurious UART/spurious SYSRQ errors,
                         // it does not address the distortion likely caused by this.
                         rockchip,pins =
-                                <4 RK_PC3 1 &pcfg_pull_down>,
+                                <4 RK_PC3 1 &pcfg_pull_none>,
                                 <4 RK_PC4 1 &pcfg_pull_none>;
                 };
         };