reenable seeding prng w/ rssi.. up preamble from 4 to 8 for reliability...

Before this, I was VERY frequently having to retry..  changing just
the gw improved things significantly, but changing it on both results
is no observable retries..  This is also the default that the example
apps in loramac uses..

irr_main.c

@@ -124,7 +124,7 @@ RadioEvents_t revents = {
 static void
 radio_seed_rng(void)
 {
-#if 0
+#if 1
 	uint32_t v;
 	int i;
 
@@ -358,7 +358,7 @@ main()
 	const uint8_t bandwidth = 0 /* 128 kHz */;
 	const uint8_t datarate = 7 /* 128 chips */;
 	const uint8_t coderate = 1 /* 4/5 */;
-	const uint8_t preambleLen = 4 /* symbols */;
+	const uint8_t preambleLen = 8 /* symbols */;
 	const uint8_t fixLen = 0 /* variable */;
 	const uint8_t crcOn = 1 /* on */;
 	const uint8_t freqHopOn = 0 /* off */;

main.c

@@ -225,7 +225,7 @@ main(void)
 	const uint8_t bandwidth = 0 /* 128 kHz */;
 	const uint8_t datarate = 7 /* 128 chips */;
 	const uint8_t coderate = 1 /* 4/5 */;
-	const uint8_t preambleLen = 4 /* symbols */;
+	const uint8_t preambleLen = 8 /* symbols */;
 	const uint8_t fixLen = 0 /* variable */;
 	const uint8_t crcOn = 1 /* on */;
 	const uint8_t freqHopOn = 0 /* off */;