phy: miphy365x: Add MiPHY365x header file for DT x Driver defines

This provides the shared header file which will be reference from both
the MiPHY365x driver and its associated Device Tree node(s).

Cc: Kishon Vijay Abraham I <kishon@ti.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>