staging: mt7621-mmc: Remove #if 0 blocks in sd.c

This patch removes #if 0 code blocks and usages of
functions defined in the #if 0 blocks in sd.c.

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