mmc: sdhci-s3c: fix the wrong number of max bus clocks

commit 5feb54a1 upstream.

We can use up to four bus-clocks; but on module remove, we didn't
disable the fourth bus clock.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>