gcc-wrapper: trim whitelist for gcc 4.7

With recent code and defconfig changes, the number warnings needing to
be ignored has gone done.  Update the wrapper accordingly.

Signed-off-by: Bryan Huntsman <bryanh@codeaurora.org>

scripts/gcc-wrapper.py

@@ -40,10 +40,7 @@ import subprocess
 # force LANG to be set to en_US.UTF-8 to get consistent warnings.
 
 allowed_warnings = set([
-    "alignment.c:327",
-    "mmu.c:602",
     "return_address.c:63",
-    "extents.c:2091",
     "kprobes.c:1483",
     "rcutree.c:1614",
     "af_unix.c:892",