hw/arm: simplify arm_load_dtb

hw/arm: simplify arm_load_dtb

In struct arm_boot_info, kernel_filename, initrd_filename and
kernel_cmdline are copied from from MachineState. This patch add
MachineState as a parameter into arm_load_dtb() and move the copy chunk
of kernel_filename, initrd_filename and kernel_cmdline into
arm_load_kernel().

Reviewed-by: Igor Mammedov <[email protected]>
Reviewed-by: Liu Jingqi <[email protected]>
Suggested-by: Igor Mammedov <[email protected]>
Signed-off-by: Tao Xu <[email protected]>
Message-Id: <20190809065731[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Acked-by: Andrew Jeffery <[email protected]>
Acked-by: Cédric Le Goater <[email protected]>
[ehabkost: include hw/boards.h again to fix build failures]
Signed-off-by: Eduardo Habkost <[email protected]>