sdhci: fix led naming

commit 5dbace0c9ba110c1a3810a89fa6bf12b7574b5a3 upstream.

Fix the led device naming for the sdhci driver.

The led class documentation defines the led name to have the
form "devicename:colour:function" while not applicable sections
should be left blank.

To comply with the documentation the led device name is changed
from "mmc*" to "mmc*::".

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>