treewide: kernel: bump some targets to 4.19

treewide: kernel: bump some targets to 4.19

Lets bump kernel to 4.19 on targets which were run tested or got ACKed
so we've enough time to make it ready for next release:

 armvirt/32 (runtested in qemu)
 armvirt/64 (runtested in qemu)
 ath79/generic (runtested on Carambola2)
 gemini/generic (runtested on DIR-685, DNS-313, SQ201, SL93512R)
 imx6/generic (runtested on Apalis)
 ipq40xx/generic (runtested on nbg6617)
 malta/be64 (runtested in qemu)
 malta/be (runtested in qemu)
 malta/le (runtested in qemu)
 malta/le64 (runtested in qemu)
 mpc85xx/generic (runtested on TL-WDR4900)
 mpc85xx/p2020 (runtested on P2020RDB)
 mvebu/cortexa53
 mvebu/cortexa72
 mvebu/cortexa10
 octeon/generic (runtested on EdgeRouter Lite)
 sunxi/cortexa53 (build tested only)
 sunxi/cortexa7 (runtested on Lime2-K)
 sunxi/cortexa8 (build tested only)
 tegra/generic
 x86/64 (runtested in qemu)

Acked-by: Zoltan HERPAI <wigyori@uid0.hu> [sunxi]
Tested-by: Linus Walleij <linus.walleij@linaro.org> [gemini]
Tested-by: Tomasz Maciej Nowak <tomek_n@o2.pl> [mvebu, tegra]
Tested-by: Daniel Engberg <daniel.engberg.lists@pyret.net> [octeon]
Tested-by: Pawel Dembicki <paweldembicki@gmail.com> [mpc85xx/generic mpc85xx/p2020]
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
Signed-off-by: Petr Štetiar <ynezz@true.cz>