fix SPIFFS_read length when reading beyond file size
fix SPIFFS_read length when reading beyond file size

EmuxEvans/spiffs,PawelDefee/spiffs,igrr/spiffs,pellepl/spiffs,ongjohn/spiffs,anusornc/spiffs,shangdawei/spiffs,pellepl/spiffs,mikewang01/spiffs,benpicco/spiffs