Fix for #1891 FT-817 CAT emulation broken for WINTEST

The change back to the original response of the real FT-817
on PTT_STATE CAT command (which is 0xff) fixes an issue with the
WINTEST program.

That hamlib only tests the bit 7 (0x80) in ft817_get_ptt does not make 0x80 a valid
answer for other programs.

cherry-pick cat fix

Author: db4ple

mchf-eclipse/drivers/cat/cat_driver.c

@@ -1286,10 +1286,11 @@ static void CatDriver_HandleCommands()
         {
             uint8_t tx_state = limit_4bits(roundf(swrm.fwd_pwr));
             tx_state |= is_splitmode() ? 0x20 : 0x00;
-            tx_state |= ts.txrx_mode == TRX_MODE_TX ? 0x00 : 0x80;
             tx_state |= swrm.vswr_dampened > 3.0 ? 0x40 : 0x00;
 
-            resp[0]= ts.txrx_mode == TRX_MODE_TX ? tx_state : 0x80;
+            // the only correct response when in rx mode is 0xff, confirmed
+            // with a real FT-817
+            resp[0]= ts.txrx_mode == TRX_MODE_TX ? tx_state : 0xff;
             if(RadioManagement_IsTxDisabled())
             {
                 resp[0] = 0xFF;