Add experimental RTX 5090 (GDDR7) memory temperature support

Reads the per-module GDDR7 DRAM sensors (FBPA DQR) directly and reports
the hotspot by default; --per-module lists each of the 8 modules.
Adds a per-device decode so the existing GDDR6/6X path is unchanged.

lib/include/gddr6.h

@@ -4,11 +4,19 @@
 
 #include <stdint.h>
 
+// How to convert a raw register read into degrees Celsius.
+enum temp_decode {
+    DECODE_ADA = 0,      // Ada/Ampere: (raw & 0xfff) / 32
+    DECODE_GDDR_MRCODE,  // Blackwell FBPA DQR: byte in bits 23:16 is a GDDR temp
+                         // MR-code; C = (code-20)*2 for code>19, else -(40-code*2)
+};
+
 struct device
 {
     uint32_t bar0;
     uint8_t bus, dev, func;
     uint32_t offset;
+    enum temp_decode decode;  // how to turn the raw reg into Celsius
     uint16_t dev_id;
     const char *vram;
     const char *arch;
@@ -27,7 +35,7 @@ struct gddr6_ctx {
 void gddr6_init(void);
 void gddr6_memory_map(void);
 void gddr6_cleanup(int signal);
-void gddr6_monitor_temperatures(void);
+void gddr6_monitor_temperatures(int per_module);
 int gddr6_detect_compatible_gpus(void);
 
 #endif // GDDR6_H