esp8266: Bump iROM size to 512k.

Needed for frozen scripts, and for future growth of binary.

esp8266/esp8266.ld

@@ -5,7 +5,7 @@ MEMORY
     dport0_0_seg : org = 0x3ff00000, len = 0x10
     dram0_0_seg :  org = 0x3ffe8000, len = 0x14000
     iram1_0_seg :  org = 0x40100000, len = 0x8000
-    irom0_0_seg :  org = 0x40210000, len = 0x5A000
+    irom0_0_seg :  org = 0x40210000, len = 0x80000
 }
 
 /* define the top of RAM */