[Fix] gpu size calculation for PIXELFORMAT_L8_A8 and mipmaps (#2350)
[Fix] gpu size calculation for PIXELFORMAT_L8_A8 and mipmaps (#2350)

* [Fix] gpu size calculation for PIXELFORMAT_L8_A8 and mipmaps

* lint fix
aidinabedi/playcanvas-engine,MicroWorldwide/PlayCanvas,playcanvas/engine,playcanvas/engine,MicroWorldwide/PlayCanvas,aidinabedi/playcanvas-engine