gcc-9: silence 'address-of-packed-member' warning

gcc-9: silence 'address-of-packed-member' warning

We already did this for clang, but now gcc has that warning too.  Yes,
yes, the address may be unaligned.  And that's kind of the point.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>