Remove all references to ioremap_nocache and replace with the LIGO_IOREMAP macro.
requested to merge jonathan-hanks/advligorts:issue_338_ioremap_cache_cannot_be_used_after_linux_5.6 into master
ioremap_nocache was renamed to ioremap at kernel 5.6. We had put code in for gpstime to allow it to build on 4.x and 5.x by use of a compatibility header which selected the proper function to call.
This request updates the rest of the ioremap_nocache calls to use the selector header file and changes the selector macro name and header file name to be more generic.