boot: fdt: Drop lmb_alloc*() typecasts

The lmb_alloc_base() returns phys_addr_t , map_sysmem() accepts
phys_addr_t as first parameter. Declare 'addr' as phys_addr_t and
get rid of the casts.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>