mtd: nand: orion: fix clk handling

The clk handling in orion_nand.c had two problems:

- In the probe function, clk_put() was called for an enabled clock,
  which violates the API (see documentation for clk_put() in
  include/linux/clk.h)

- In the error path of the probe function, clk_put() could be called
  twice for the same clock.

In order to clean this up, use the managed function devm_clk_get() and
store the pointer to the clk in the driver data.

Fixes: baffab28

 ('ARM: Orion: fix driver probe error handling with respect to clk')
Cc: <stable@vger.kernel.org> # v4.5+
Signed-off-by: Simon Baatz <gmbnomis@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>