Fix erase size in ESP.eraseConfig
Fix erase size in ESP.eraseConfig

SDK uses final 4 sectors of flash for configuration data.
ESP.eraseConfig would only erase 2 sectors, so in some cases of
corrupted data ("system param error"), users could not fix the issue
using ESP.eraseConfig, and had to use esptool instead.

Thanks @HugoML for reporting this.

lrmoreno007/Arduino,jes/Arduino,wemos/Arduino,Adam5Wu/Arduino,jes/Arduino,Adam5Wu/Arduino,Lan-Hekary/Arduino,Adam5Wu/Arduino,me-no-dev/Arduino,hallard/Arduino,me-no-dev/Arduino,jes/Arduino,esp8266/Arduino,lrmoreno007/Arduino,Juppit/Arduino,wemos/Arduino,sticilface/Arduino,jes/Arduino,lrmoreno007/Arduino,Lan-Hekary/Arduino,Juppit/Arduino,wemos/Arduino,wemos/Arduino,esp8266/Arduino,me-no-dev/Arduino,sticilface/Arduino,hallard/Arduino,sticilface/Arduino,hallard/Arduino,lrmoreno007/Arduino,Adam5Wu/Arduino,esp8266/Arduino,lrmoreno007/Arduino,me-no-dev/Arduino,me-no-dev/Arduino,Lan-Hekary/Arduino,sticilface/Arduino,esp8266/Arduino,hallard/Arduino,Juppit/Arduino,jes/Arduino,Lan-Hekary/Arduino,wemos/Arduino,Adam5Wu/Arduino,esp8266/Arduino,Juppit/Arduino,Juppit/Arduino,sticilface/Arduino,Lan-Hekary/Arduino,hallard/Arduino