usb: ohci-ep93xx: use devm_clk_get()

Use devm_clk_get() to make the code a bit cleaner and simpler.

This also fixes a bug where a clk_put() is not done if usb_add_hcd()
fails.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>