staging: mt7621-mmc: Fix lines over 80 characters in dbg.c

This patch fixes lines over 80 characters in dbg.c.
Issue found by checkpatch.

Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>