Cleanup the ohci-ep93xx driver.

1) Use the usb.h dbg() macro instead of pr_debug() so that
   the source filename is prefixed to the message and it is
   terminated with a linefeed.

2) Add error handling for the clk_get() call.

3) Update clkdev support so that the usb clock is matched by
   the dev_id instead of the con_id.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>