anv/pipeline: Only consider double elements which actually exist

The brw_vs_prog_data::double_inputs_read field comes directly from
shader_info::double_inputs which may contain inputs which are not
actually read.  Instead of using it directly, AND it with inputs_read
which is only things which are read.  Otherwise, we may end up
subtracting too many elements when computing elem_count.

Cc: mesa-stable@lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103241


Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
(cherry picked from commit 7b267418)