kernel/linux: fix packed attribute in exported headers

UBI headers (and maybe others as well) are broken because the 'packed'
attribute is not sanitised when the headers are exported to userspace.

Apply the fix from upstream:
https://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=f210735fe2f17a6225432ee3d1239bcf23a8659c

(Also, buildroot does the same, BTW)

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 syntax: glob

 # Generated files

 Makefile

 *ct-ng*

 docs/*ct-ng*.1

 docs/*ct-ng*.1.gz

 paths.mk

 scripts/crosstool-NG.sh

 scripts/saveSample.sh

 scripts/showTuple.sh

 kconfig/conf

 kconfig/?conf

 kconfig/**.o

 kconfig/**.dep

 config/configure.in

 config.gen/

 .config

 .config.2

 # Temporaries

 .*.swp

 build.log

 .config.old

 # This is the place where toolchains are built

 .build/

 # .. and the legacy location

 targets/