uboot-imx

checkpatch.pl: Add warning for new __packed additions

While there are valid reasons to use __packed, often the answer is that
you should be doing something else here instead.

This reintroduces the changes of
f503cc49a570 (Add warning for new __packed additions)

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>