mmc: stm32_sdmmc2: protect against unsupported modes

The UHS modes for SD, HS200 and HS400 modes for eMMC are not supported
by the stm32_sdmmc2 driver.
Make it clear by removing the corresponding caps after parsing the DT.

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>