qcacmn: Resolve difference in pointer signedness

The control buffer element of socket buffer structure (sk_buff)
is of the data type char and the virtual address element of network
buffer control block structure is of the type unsigned char. The
current prototypes cause this pointer assignment with different
signedness.
Fix this by using appropriate type in the API definition.

Change-Id: Ic20ca29ce5d26a134ef295663632a5b7fd420954
CRs-Fixed: 3269690

qdf/linux/src/i_qdf_nbuf.h

@@ -2236,7 +2236,7 @@ static inline uint32_t __qdf_nbuf_tcp_seq(struct sk_buff *skb)
  *
  * Return: data pointer to typecast into your priv structure
  */
-static inline uint8_t *
+static inline char *
 __qdf_nbuf_get_priv_ptr(struct sk_buff *skb)
 {
 	return &skb->cb[8];