USB: EHCI: make ehci-platform use dev_err() instead of pr_err()

This patch converts the ehci-platform driver to make use of the dev_err()
functions instead of pr_err().

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>