scripts: Add a warning into gcc-wrapper white list

Add following warning into white list of warnings to
avoid compilation break.
"The right operand of shift is greater than or equal to the length
in bits of the promoted left operand (result is folded to zero)
[-Wundefined-optimized] error, forbidden warning: page_alloc.c:7248"

Change-Id: Ifdd3baf5cfedb8c5f1b0e8b97d173ffbb1da4676
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>