st/dri: remove leftover local variable

Left over from the cleanup in 6ccc435e7a "pipe-loader: move dup(fd)
within pipe_loader_drm_probe_fd"

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/gallium/state_trackers/dri/dri2.c

@@ -2205,7 +2205,6 @@ dri_kms_init_screen(__DRIscreen * sPriv)
    struct dri_screen *screen;
    struct pipe_screen *pscreen = NULL;
    uint64_t cap;
-   int fd;
 
    screen = CALLOC_STRUCT(dri_screen);
    if (!screen)