ARM: dts: stih410-family: Add missing reset_names for mmc1 node

reset-names property is needed to use the reset
API for STi sdhci driver.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>