ARM: mvebu: remove clock-frequency from Armada 38x SDHCI Device Tree node

For proper operation of Armada 38x SDHCI controller proper 'clocks' property
is sufficient. Therefore it is not useful to keep an additional
'clock-frequency' property in SDHCI controller node of board-level Device Tree
file for Armada 385 DB.

This commit gets rid of useless 'clock-frequency' property.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lkml.kernel.org/r/1415980652-7429-4-git-send-email-mw@semihalf.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>