staging: rtl8188eu: core: constify local structure

Constify the static struct RTW_CHANNEL_PLAN_MAP_REALTEK_DEFINE.

The only other instance was one of its properties being assigned to a
variable:
Index2G = RTW_CHANNEL_PLAN_MAP_REALTEK_DEFINE.Index2G;

Therefore this is a good candidate for constification.

Running size did not show any difference:
Before/After:
text    data     bss     dec     hex filename
44122     408    2974   47504    b990

Lastly, break up the long line to fix the checkpatch warning and conform
to kernel coding style.
Signed-off-by: Elizabeth Ferdman <gnudevliz@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/core/rtw_mlme_ext.c

@@ -133,7 +133,9 @@ static struct rt_channel_plan_map	RTW_ChannelPlanMap[RT_CHANNEL_DOMAIN_MAX] = {
 	{0x03},	/* 0x41, RT_CHANNEL_DOMAIN_GLOBAL_DOAMIN_2G */
 };
 
-static struct rt_channel_plan_map RTW_CHANNEL_PLAN_MAP_REALTEK_DEFINE = {0x03}; /* use the combination for max channel numbers */
+static const struct rt_channel_plan_map RTW_CHANNEL_PLAN_MAP_REALTEK_DEFINE = {
+	0x03
+}; /* use the combination for max channel numbers */
 
 /*
  * Search the @param channel_num in given @param channel_set