Wlan: Correct condition check in csrRoamGetIbssStartChannelNumber50

In csrRoamGetIbssStartChannelNumber50(), after the unsuccessful search
for Ibss channel in csrStartIbssChannels50[] and roam.validChannelList[],
incorrect logic is used to find the first 11a channel.

Correcting the logic to use idxValidChannels and roam.validChannelList[]
for finding the first 11a channel.

Change-Id: Ia84e86ca548a8749b88179dd7b8cc8270ba6c855
CRs-Fixed: 737734
diff --git a/CORE/SME/src/csr/csrApiRoam.c b/CORE/SME/src/csr/csrApiRoam.c
index 73538c2..e89761c 100644
--- a/CORE/SME/src/csr/csrApiRoam.c
+++ b/CORE/SME/src/csr/csrApiRoam.c
@@ -11568,9 +11568,9 @@
         {
             for ( idxValidChannels = 0; idxValidChannels < len ; idxValidChannels++ )
             {
-                if ( CSR_IS_CHANNEL_5GHZ(pMac->roam.validChannelList[ idx ]) )   // the max channel# in 11g is 14
+                if ( CSR_IS_CHANNEL_5GHZ(pMac->roam.validChannelList[ idxValidChannels ]) )   // the max channel# in 11g is 14
                 {
-                    channel = csrStartIbssChannels50[ idx ];
+                    channel = pMac->roam.validChannelList[ idxValidChannels ];
                     break;
                 }
             }