Use dev_read_addr_ptr() and dev_read_addr_index_ptr() which support both
live device tree and flat DT backends, avoiding direct dependency on
devfdt_* helpers.
While at here, also use ofnode_read_s32_default() to replace
fdtdec_get_int().
No functional changes.
Signed-off-by: Peng Fan <peng.fan@nxp.com>