mfd: ab2100-otp: Remove pointless 'out of memory' error message

WARNING: Possible unnecessary 'out of memory' message
+       if (!otp) {
+               dev_err(&pdev->dev, "could not allocate AB3100 OTP device\n");

total: 0 errors, 1 warnings, 250 lines checked

Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>