env: mmc: Make the debug messages play a little nicer

env: mmc: Make the debug messages play a little nicer

Since we have global messages to indicate what's going on, the custom
messages in the environment drivers only make the output less readable.

Make MMC play a little nicer by removing all the extra \n and formatting
that is redundant with the global output.

Reviewed-by: Andre Przywara <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Signed-off-by: Maxime Ripard <[email protected]>
Reviewed-by: Jaehoon Chung <[email protected]>