kenwood.h: fix typo

looks like `last_mode_pc` was missing a character on the type. This was caught by compiling on musl libc, where `mode_t` wasn't available from any of the other includes.

rigs/kenwood/kenwood.h

@@ -183,7 +183,7 @@ struct kenwood_priv_data
     int save_k2_ext_lvl; // so we can restore to original
     int save_k3_ext_lvl; // so we can restore to original -- for future use if needed
     int voice_bank; /* last voice bank send for use by stop_voice_mem */
-    mode_t last_mode_pc; // last mode memory for PC command
+    rmode_t last_mode_pc; // last mode memory for PC command
     int power_now,power_min,power_max;
 };