kexec: fix build for arm

kexec: fix build for arm

Add a patch equivalent to upstream commit 1574ff1aae4 (arm: include
phys_to_virt.h and iomem.h in distribution).

Fixes:
http://autobuild.buildroot.net/results/bf9/bf939477cce6a5c333ee579006b9aa4856acd604/
http://autobuild.buildroot.net/results/8a7/8a7407afcf47326aadbce0b9157442dae9558ded/
http://autobuild.buildroot.net/results/ec2/ec26f1dd97f1e861e401d2709a243ae55bd6f022/

Cc: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>