fix: if mask not present, opencl kernel fails with divide by 0

If utilizing micro kernel version of sdpa without an attention mask, the opencl kernel will fail to compile with a divide by zero error. This remove the `msk` index computation in the absence of the mask to avoid the error and allow micro kernel sdpa to function w/o the mask as intended.

src/gpu/intel/ocl/micro_sdpa.cl

@@ -202,7 +202,9 @@ micro_sdpa(const global half *K, const global half *Q, const global half *V,
     Q += QRY_OFF(b1, b0, 0, 0);
     V += VAL_OFF(b1, b0 / KV_GROUP_SIZE, 0, 0);
     A += DST_OFF(b1, b0, 0, 0, 0);
+#if WITH_ATTN_MASK
     msk += MSK_OFF(b1 % MSK_D0, b0 % MSK_D1, 0, 0);
+#endif
 
     /* Load Q tile, destined for SLM */
     q_tile_type Q_tile;