dts: arm: st: f0: Include STM32F070 dts in STM32F072 dts

Add successive inclusion for STM32F072 dts by including
STM32F070 dts instead of STM32F0 dts.
This allows to reuse the definition of
 - Flash
 - SPI
 - USB
from the new parent.

Signed-off-by: Guillaume Gautier <guillaume.gautier-ext@st.com>