dm: core: add ofnode_count_phandle_with_args()

dm: core: add ofnode_count_phandle_with_args()

This function is usefull to get phandle number contained
in a property list.
For example,  this allows to allocate the right amount
of memory to keep clock's reference contained into the
"clocks" property.

To implement it, either of_count_phandle_with_args() or
fdtdec_parse_phandle_with_args() are used respectively
for live tree and flat tree.
By passing index = -1, these 2 functions returns the
number of phandle contained into the property list.

Add also the dev_count_phandle_with_args() based on
ofnode_count_phandle_with_args()

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>