nvmem: imx-ocotp: clear error bit after reading locked values

When reading a "read locked" value from the OCOTP controller on i.MX6
SoC's an error bit is set. This bit has to be cleared by software before
any new write, read or reload access can be issued.

Therefore clear it after we detect such an "locked read".

Signed-off-by: Richard Leitner <richard.leitner@skidata.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>