mmc: make MAN_BKOPS_EN message a debug

commit 4ec96b4c upstream.

IMO this info is only useful for developers. Most users won't need this
information, since there is not much they can do about it.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I8a9a0eefb0158b4e077fe9485faa89c497fe190f
Signed-off-by: Lee Jones <joneslee@google.com>