mmc: mediatek: free the ext_csd when mmc_get_ext_csd success

If mmc_get_ext_csd success, the ext_csd are not freed.
Add the missing kfree() calls.

Signed-off-by: Wenbin Mei <wenbin.mei@mediatek.com>
Fixes: c4ac38c6 ("mmc: mtk-sd: Add HS400 online tuning support")
Link: https://lore.kernel.org/r/20211207075013.22911-1-wenbin.mei@mediatek.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>