regulator: ti-abb: Convert to use devm_ioremap_resource

Commit 75096579 ("lib: devres: Introduce devm_ioremap_resource()")
introduced devm_ioremap_resource() and deprecated the use of
devm_request_and_ioremap().

While at it, remove the error message as devm_ioremap_resource prints a similar
error message.

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>