kernel: RTC + tsadc ported (open-source, from vendor source); npu/rga plans

RTC: ported the vendor rockchip,rv1106-rtc driver (rtc-rockchip.c) to 6.18 — one
API delta (rtc_register_device -> devm_rtc_register_device). Verified on
warden-c8a3: /dev/rtc0 registers and reads.

tsadc thermal: ported the rv1106 data + rk_tsadcv9_initialize + the TSADCV9/VOGRF
macros + code table from the vendor; adapted .chn_id[SENSOR_CPU] -> .chn_offset
for 6.18. Verified: thermal_zone0 "soc-thermal" reads 39.8 C.

i2s-tdm: rv1126 fallback compatible added (DAI builds; sound card needs the acodec
port next). saradc still -22 (clk-rv1106 SARADC divider — deferred).

Includes the NPU + RGA open-source port plans (research): rknpu kernel driver is a
small port (RV1106 config already in the vendor driver; 4 dead-code headers need
compat stubs) but no open userspace exists for this NPU gen; RGA = port the vendor
char-dev rga3 driver (WardenOS's librga uses /dev/rga, not V4L2), + a cma pool +
hrtimer_setup. All ports are open source (vendor C source / mainline siblings).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017wB8KB3MMQztRDXCMCkPrf

kernel/rv1106-enablement/dts/rv1106-warden.dts

@@ -146,3 +146,16 @@
 	status = "okay";
 	dr_mode = "otg";
 };
+
+/* --- sweep: RTC + thermal (tsadc) + I2S audio DAI --- */
+&rtc {
+	status = "okay";
+};
+
+&tsadc {
+	status = "okay";
+};
+
+&i2s0_8ch {
+	status = "okay";
+};