mesa: bptc fixes for decompress rgba_unorm/rgb_float
Save bit_offset between iterations.
Save bit_offset between iterations fixes for piglit:
- LIBGL_ALWAYS_SOFTWARE=true GALLIUM_DRIVER=softpipe piglit/bin/bptc-float-modes
- LIBGL_ALWAYS_SOFTWARE=true GALLIUM_DRIVER=llvmpipe piglit/bin/bptc-float-modes
Memset to zero in reserved mode for rgba_unorm fixes for VK-GL-CTS with libvulkan_val:
- dEQP-VK.texture.compressed.bc7_unorm_block_2d_pot
- dEQP-VK.texture.compressed.bc7_srgb_block_2d_pot
- dEQP-VK.texture.compressed.bc7_unorm_block_2d_npot
- dEQP-VK.texture.compressed.bc7_srgb_block_2d_npot