i2c: nomadik: Don't use IS_ERR for devm_ioremap

devm_ioremap() returns NULL on error, not an error.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org