TP-LINK WR740N Can't install luci-app-sqm package

@Modrate

It's because of space issues, check my custom builds include SQM with support for TP-LINK routers with 4MB Flash

LEDE 17.01.6 complete custom build
Optimized build LEDE 17.01 / OpenWrt 18.06 / libreCMC for "small devices"