Kbuild: suppress packed-not-aligned warning for default setting only

Kbuild: suppress packed-not-aligned warning for default setting only

commit 321cb0308a9e76841394b4bbab6a1107cfedbae0 upstream.

gcc-8 reports many -Wpacked-not-aligned warnings. The below are some
examples.

./include/linux/ceph/msgr.h:67:1: warning: alignment 1 of 'struct
ceph_entity_addr' is less than 8 [-Wpacked-not-aligned]
 } __attribute__ ((packed));

./include/linux/ceph/msgr.h:67:1: warning: alignment 1 of 'struct
ceph_entity_addr' is less than 8 [-Wpacked-not-aligned]
 } __attribute__ ((packed));

./include/linux/ceph/msgr.h:67:1: warning: alignment 1 of 'struct
ceph_entity_addr' is less than 8 [-Wpacked-not-aligned]
 } __attribute__ ((packed));

This patch suppresses this kind of warnings for default setting.

Signed-off-by: Xiongfeng Wang <xiongfeng.wang@linaro.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[sw0312.kim: cherry-pick stable linux-3.18.y commit 7b1fe42a5e15 for gcc 9 build]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Change-Id: Id1e9b809a6b71bfca34221617e3fed3e2a379abc