Log when a device on a mmc bus is hw reset

The original message was a debug message, turned off by default, so
we couldn't tell if it was being invoked when we had emmc errors.
Change it to KERN_WARN level, always print it, and improve the
actual error message.

Change-Id: I909a106470e139402ba2764d486bd3aa464a6cc6
Signed-off-by: Ken Sumrall <ksumrall@android.com>