translate: do not clamp element index in generic_run

translate: do not clamp element index in generic_run

The buffer max_index value in translate_generic struct is relevant for
indexed draw only. So do not clamp the element index in generic_run() as it
is called for non-indexed draw only.
This patch passes index_size to the common generic_run_one function
so index clamping is only performed when a non-zero index_size is specified.

This fixes a text selection bug with kitty terminal emulator running on ARM
when it falls back to the generic translate path for unsigned byte vertex
array.

cc: mesa-stable

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22568>