SDL_render_sw.c: fix -Wshadow warnings.
diff --git a/src/render/software/SDL_render_sw.c b/src/render/software/SDL_render_sw.c
index 6ce921a..1aaffac 100644
--- a/src/render/software/SDL_render_sw.c
+++ b/src/render/software/SDL_render_sw.c
@@ -862,7 +862,6 @@
 
                     /* Apply viewport */
                     if (drawstate.viewport->x || drawstate.viewport->y) {
-                        int i;
                         SDL_Point vp;
                         vp.x = drawstate.viewport->x;
                         vp.y = drawstate.viewport->y;
@@ -886,7 +885,6 @@
 
                     /* Apply viewport */
                     if (drawstate.viewport->x || drawstate.viewport->y) {
-                        int i;
                         SDL_Point vp;
                         vp.x = drawstate.viewport->x;
                         vp.y = drawstate.viewport->y;