uio: pruss: add clk_disable()

pruss_probe() enables gdev->pruss_clk, but there is no clk_disable()
in the driver.

The patch adds clk_disable() to pruss_cleanup() and error handling for
clk_enable().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>