When testing SD hotplug automatically, I got bunch of
useless log like this:

[  588.357838] mmc0: card 0007 removed
[  589.492664] rockchip-iodomain ff770000.syscon:io-domains: Setting to 3300000 done
[  589.500698] vccio_sd: ramp_delay not set
[  589.504817] rockchip-iodomain ff770000.syscon:io-domains: Setting to 3300000 done
[  589.669705] rockchip-iodomain ff770000.syscon:io-domains: Setting to 3300000 done
[  589.677593] vccio_sd: ramp_delay not set
[  589.681581] rockchip-iodomain ff770000.syscon:io-domains: Setting to 1800000 done
[  590.032820] dwmmc_rockchip ff0c0000.dwmmc: Successfully tuned phase to 140
[  590.039725] mmc0: new ultra high speed SDR50 SDHC card at address 0007
[  590.046641] mmcblk0: mmc0:0007 SD32G 29.3 GiB
[  590.052163]  mmcblk0: p1

Moreover the code is intent to print the 'uV' for debug but
later print it using dev_info. It looks more like to me that
it should be the real intention of the code. Anyway, let's
mark this verbose log as debug message.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>