mesa: remove stale comment

This line stopped making sense in the great sed
replace of commit f9995b30756140724f41daf963fa06167912be7f

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
mesa: remove outdated comment

No such argument exists since this commit:

commit 92f3fca0ea429dcf07123e63447449db53308266
Author:     Ian Romanick <ian.d.romanick@intel.com>
AuthorDate: Sun Aug 21 17:23:58 2011 -0700
Commit:     Ian Romanick <ian.d.romanick@intel.com>
CommitDate: Tue Aug 23 14:52:09 2011 -0700

    mesa: Remove target parameter from dd_function_table::BufferSubData

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
mesa: remove handcounted magic number

Also make it a compile-time error with STATIC_ASSERT.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Revert "llvmpipe: increase number of subpixel bits to eight"

This reverts commit 755c11dc5e94f17097c186edaaa39d818396f14c.
We agreed that this is band-aid that's not very useful and
the proper solution is to rewrite the rasterization algo
so that it operates on 64 bit values.

Signed-off-by: Zack Rusin <zackr@vmware.com>