turnip: update "fetchsize" value to match fdl6_layout changes

turnip: update "fetchsize" value to match fdl6_layout changes

It seems this is actually a "minimum pitch" value. For example
TFETCH6_2_BYTE means a minimum pitch of 128 bytes for mipmap levels.

This fixes breakage with compressed formats. For example this test:

dEQP-VK.pipeline.sampler.view_type.2d.format.eac_r11_snorm_block.mipmap.linear.lod.equal_min_3_max_3

Fixes: a34b3fa198a4f ("freedreno/fdl: Align after dividing by block size")
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5009>