i965/tex_image: Avoid the ASTC LDR workaround on gen9lp

Both the internal documentation and the results of testing this in the
CI suggest that this is unnecessary. Add the fixes tag because this
reduces an internal benchmark's startup time by about 17 seconds
(reported by Eero).

Fixes: 710b1d2e "i965/tex_image: Flush certain subnormal ASTC channel values"
Tested-by: Eero Tamminen <eero.t.tamminen@intel.com>
Acked-by: Kenneth Graunke <kenneth@whitecape.org>
(cherry picked from commit 3e56e464)