devicetree: Fix DT_FOREACH_PROP_ELEM_SEP example

Change the DT_FOREACH_PROP_ELEM_SEP example documented to use the
correct macro GPIO_DT_SPEC_GET_BY_IDX() instead of
GPIO_DT_SPEC_BY_IDX().

Signed-off-by: Keith Short <keithshort@google.com>
1 file changed