serial: stm32x7: remove stm32f7-usart and stm32h7-usart compatible

This patch remove the extra compatibility string "st,stm32h7-usart"
and "st,stm32f7-usart" to avoid confusion, save some time & space.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Vikas Manocha <vikas.manocha@st.com>
2 files changed