Performance regression with large textures on SA8155P

Performance has regressed significantly with scenes utilizing large textures between 6.1.0 final and 6.1.1 / 6.2.0 snapshots.

Performance regression becomes significant with larger than the smallest mesh, if texture size is 4096x4096. For example, a test set with 10 Medium models, point light, IBL and no AA is running 16 FPS with 6.2 snapshot and 29 FPS on 6.1 final.

See https://qtcompany-my.sharepoint.com/:x:/g/personal/tomi_korpipaa_qt_io/EaZdyv1ScBlOgUCGFYybImUBPQuCMVpXQEGr0cvdG2daJw?e=dn6hsP for quick reference.

Full test sets available here https://intranet.qt.io/display/QTRD/Qt+Quick+3D+performance+knowledge+base Check the benchmark_result_testeset_benchmarkset_offscreen_qt_part1-*.txt -files.