treewide: Use fdt_create_phandle() where appropriate

Replace fdt_alloc_phandle() with subsequent fdt_set_phandle() by
fdt_create_phandle().

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
Cc: Aaron Williams <awilliams@marvell.com>
Cc: Ramon Fried <rfried.dev@gmail.com>
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>