[Controls] Link only SDK so we don't brake the sample (#372)

Xamarin.Forms.ControlGallery.iOS/Xamarin.Forms.ControlGallery.iOS.csproj

@@ -24,7 +24,7 @@
     <WarningLevel>4</WarningLevel>
     <ConsolePause>false</ConsolePause>
     <MtouchArch>i386, x86_64</MtouchArch>
-    <MtouchLink>Full</MtouchLink>
+    <MtouchLink>SdkOnly</MtouchLink>
     <MtouchDebug>True</MtouchDebug>
     <CodesignEntitlements>Entitlements.plist</CodesignEntitlements>
     <MtouchSdkVersion></MtouchSdkVersion>