memory: brcmstb_dpfe: simplify platform_get_resource_byname()

Use devm_platform_ioremap_resource_byname() instead of
platform_get_resource_byname() and devm_ioremap_resource().

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220419142859.380566-6-krzysztof.kozlowski@linaro.org