mmc: block: add newline to sysfs display of force_ro

commit 0031a98a85e9fca282624bfc887f9531b2768396 upstream.

Make force_ro consistent with other sysfs entries.

Fixes: 371a689f ('mmc: MMC boot partitions support')
Cc: Andrei Warkentin <andrey.warkentin@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>