mmc: Check support for TRIM operations

When secure/insecure TRIM operations are supported.
When used as erase command argument it applies the
erase operation to write blocks instead of erase
groups.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>