staging: mt7621-mmc: Fix debug macro ERR_MSG and its usages

Replace all usages of ERR_MSG with with dev_<level> without __func__
or __LINE__ or current->comm and current->pid. Remove the do {}
while(0) loop for the single statement macro. Delete commented
ERR_MSG() usage. Drop ERR_MSG from dbg.h. Issue found by checkpatch.

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