glsl: fix heap-buffer-overflow

The `end+1` skips the ']', whereas the `strlen+1` includes the final
'\0' in the move to terminate the string.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
(cherry picked from commit fc27181f9e51441a26b7eb4f62794b5e9a994644)
1 file changed