vrend: Create gbm bo with default modifier
Currently virgrenderer creates gbm bo with no modifiers and rely on platform supported modifier/tiling selection. This leads to failures during MMAP(GTT ioctl) on platforms where specific tiling is selected and no h/w detiling available.
The commit sets linear modifier as default to create gbm bo and resolves the discrepancies with expected golden values during CtsNativeHardware and dEQP-GLES3 tests.