glsl: fix inequality in set_program_uniform()

We were off by one when checking for too many uniform values.
diff --git a/src/mesa/shader/shader_api.c b/src/mesa/shader/shader_api.c
index 828d3f0..afd2c2a 100644
--- a/src/mesa/shader/shader_api.c
+++ b/src/mesa/shader/shader_api.c
@@ -1660,7 +1660,7 @@
       for (k = 0; k < count; k++) {
          GLfloat *uniformVal;
 
-         if (offset + k > slots) {
+         if (offset + k >= slots) {
             /* Extra array data is ignored */
             break;
          }