add a not device managed memremap_pages v3

Hi Dan and Jason, Bharata has been working on secure page management for kvmppc guests, and one I thing I noticed is that he had to fake up a struct device just so that it could be passed to the devm_memremap_pages instrastructure for device private memory. This series adds non-device managed versions of the devm_request_free_mem_region and devm_memremap_pages functions for his use case. Changes since v2: - improved changelogs that the the v2 changes into account Changes since v1: - don't overload devm_request_free_mem_region - export the memremap_pages and munmap_pages as kvmppc can be a module