wlan: More checkpatch fixes for WLAN prima driver

This patch has fixes for the following checkpatch issues:
1 ERROR: Use of strchr is deprecated: use strnchr instead.
2 WARNING: simple_strtol is obsolete, use kstrtol instead
3 WARNING: simple_strtoul is obsolete, use kstrtoul instead

Change-Id: Ib75b587f60fa8bd950d31da8ece5b8a575e66953
CR-Fixed: NA
diff --git a/CORE/HDD/src/wlan_hdd_dp_utils.c b/CORE/HDD/src/wlan_hdd_dp_utils.c
index f5b3117..970739e 100644
--- a/CORE/HDD/src/wlan_hdd_dp_utils.c
+++ b/CORE/HDD/src/wlan_hdd_dp_utils.c
@@ -197,6 +197,7 @@
    int i;
    int k;
    char temp[3] = {0};
+   int rv;
 
    //18 is MAC Address length plus the colons
    if ( !pSrcMac && (length > 18 || length < 18) )
@@ -207,7 +208,9 @@
    while ( i < length )
    {
        memcpy(temp, pSrcMac+i, 2);
-       pDescMac[k++] = (char)simple_strtoul (temp, NULL, 16);
+       rv = kstrtou8(temp, 16, &pDescMac[k++]);
+       if (rv < 0)
+           return VOS_STATUS_E_FAILURE;
        i += 3;
    }