esp8266/esp8266.ld: Increase firmware image size to 0x90000 (576K).

Of them, 0x87000 is irom0 segment. This is required to ship increasing number of modules and examples developed in teh course of ESP8266 port project.

Author: pfalcon

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 = 0x40209000, len = 0x80000
+ irom0_0_seg : org = 0x40209000, len = 0x87000
 }
 
 /* define the top of RAM */