vulkan: more mul mat optimizations (#18533)

* q4_k

* q5_k

* q2_k

* q4_1

* q5_1

* better buf index

ggml/src/ggml-vulkan/vulkan-shaders/dequant_funcs.glsl

@@ -462,7 +462,8 @@ vec2 get_dm(uint ib, uint a_offset) {
 
 #if defined(DATA_A_Q4_1) || defined(DATA_A_Q5_1)
 vec2 get_dm(uint ib, uint a_offset) {
-    return vec2(float(data_a[a_offset + ib].d), float(data_a[a_offset + ib].m));
+    const vec2 dm = vec2(data_a_packed32[a_offset + ib].dm);
+    return dm;
 }
 #endif