staging: r8188eu: simplify complex pointer casting

Pointers to structures udphdr and dhcpMessage are derived by casting
adjacent pointers with size_t. Such typecast of pointer using size_t
is not preferred. The code looks complex and delicate. Simplify such
casting by utilizing generic "void *" casting.
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Deepak R Varma <drv@mailo.com>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Link: https://lore.kernel.org/r/1428580d09a9916899209c9278dca40ee2d297d3.1667755987.git.drv@mailo.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/core/rtw_br_ext.c

@@ -610,12 +610,11 @@ void dhcp_flag_bcast(struct adapter *priv, struct sk_buff *skb)
 			struct iphdr *iph = (struct iphdr *)(skb->data + ETH_HLEN);
 
 			if (iph->protocol == IPPROTO_UDP) { /*  UDP */
-				struct udphdr *udph = (struct udphdr *)((size_t)iph + (iph->ihl << 2));
+				struct udphdr *udph = (void *)iph + (iph->ihl << 2);
 
 				if ((udph->source == htons(CLIENT_PORT)) &&
 				    (udph->dest == htons(SERVER_PORT))) { /*  DHCP request */
-					struct dhcpMessage *dhcph =
-						(struct dhcpMessage *)((size_t)udph + sizeof(struct udphdr));
+					struct dhcpMessage *dhcph = (void *)udph + sizeof(struct udphdr);
 					u32 cookie = be32_to_cpu((__be32)dhcph->cookie);
 
 					if (cookie == DHCP_MAGIC) { /*  match magic word */