lib: utils: Add fdt_parse_clint_node() function

We add fdt_parse_clint_node() function which will be used by
fdt_ipi_clint and fdt_timer_clint drivers to parse CLINT details
from DT node.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>