lib: devres: add convenience function to remap a resource

Almost every platform_driver does the three steps get_resource,
request_mem_region, ioremap. This does not only lead to a lot of code
duplication, but also a huge number of similar error strings and
inconsistent error codes on failure. So, introduce a helper function
which simplifies remapping a resource and make it hard to do something
wrong and add documentation for it.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index d79aead..10c64c8 100644
--- a/Documentation/driver-model/devres.txt
+++ b/Documentation/driver-model/devres.txt
@@ -262,6 +262,7 @@
   devm_ioremap()
   devm_ioremap_nocache()
   devm_iounmap()
+  devm_request_and_ioremap() : checks resource, requests region, ioremaps
   pcim_iomap()
   pcim_iounmap()
   pcim_iomap_table()	: array of mapped addresses indexed by BAR