Enable CONFIG_DFS for RTL8821CE adapters, to support 5Ghz bands only allowed with DFS.

DFS (as client, not as AP) is supported by the Windows driver, and it seems to be implemented in this driver too, just disabled.

This fixes issue #34. Thanks to @tomaspinho for pointing me in the right direction.

include/hal_ic_cfg.h

@@ -234,6 +234,7 @@
 #ifdef CONFIG_RTL8821C
 	#undef RTL8821C_SUPPORT
 	#define RTL8821C_SUPPORT				1
+	#define CONFIG_DFS	/* Enable 5G band 2&3 channel */
 	#ifndef CONFIG_FW_C2H_PKT
 		#define CONFIG_FW_C2H_PKT
 	#endif