mmc: core: Remove unnecessary scale debugfs entry

Current scale debugfs entry is quite unstable and used barely.
Hardware cmd timeout and some other issues are being seen when trying to
modify the scale entry.
Remove unnecessary scale debugfs entry to avoid such issues.

Change-Id: I9486a9fe7498ba1855153202415fca80debb13f9
Signed-off-by: Sarthak Garg <sartgarg@codeaurora.org>