checkpatch: add ignore for network block comment style checking

When use checkpatch.pl to check network related patch, it will report
--->8---
WARNING: networking block comments don't use an empty /* line,
use /* Comment...
---<8---

So, add --ignore NETWORKING_BLOCK_COMMENT_STYLE into .checkpatch.conf
This will help to keep all driver include network related driver use
the same comment style

Signed-off-by: Bo Shen <voice.shen@atmel.com>

.checkpatch.conf

@@ -18,3 +18,6 @@
 
 # Not Linux, so we don't recommend usleep_range() over udelay()
 --ignore USLEEP_RANGE
+
+# Ignore networking block comment style
+--ignore NETWORKING_BLOCK_COMMENT_STYLE