ice: switch: unobscurify bitops loop in ice_fill_adv_dummy_packet()

A loop performing header modification according to the provided mask
in ice_fill_adv_dummy_packet() is very cryptic (and error-prone).
Replace two identical cast-deferences with a variable. Replace three
struct-member-array-accesses with a variable. Invert the condition,
reduce the indentation by one -> eliminate line wraps.

Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Marcin Szycik <marcin.szycik@linux.intel.com>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/ice/ice_switch.c

@@ -5810,13 +5810,15 @@ ice_fill_adv_dummy_packet(struct ice_adv_lkup_elem *lkups, u16 lkups_cnt,
 		 * indicated by the mask to make sure we don't improperly write
 		 * over any significant packet data.
 		 */
-		for (j = 0; j < len / sizeof(u16); j++)
-			if (lkups[i].m_raw[j])
-				((u16 *)(pkt + offset))[j] =
-					(((u16 *)(pkt + offset))[j] &
-					 ~lkups[i].m_raw[j]) |
-					(lkups[i].h_raw[j] &
-					 lkups[i].m_raw[j]);
+		for (j = 0; j < len / sizeof(u16); j++) {
+			u16 *ptr = (u16 *)(pkt + offset);
+			u16 mask = lkups[i].m_raw[j];
+
+			if (!mask)
+				continue;
+
+			ptr[j] = (ptr[j] & ~mask) | (lkups[i].h_raw[j] & mask);
+		}
 	}
 
 	s_rule->pdata.lkup_tx_rx.hdr_len = cpu_to_le16(pkt_len);