scripts: gcc-wrapper: Add exceptions for netfilter failures with gcc-4.6.3

Compiling the kernel with gcc-4.6.3 generates multiple forbidden
warnings for netfilter. Adding them to the allowed warnings list.

Change-Id: I7214d8c1bb59c99e2422eaac2a820fb43cf62b1e
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>
(cherry picked from commit 660d3ffb16a8ee7c5693d745a8588c991035c8e7)