tools/testing/nvdimm: Fix mock support for ioremap

After commit d092a870 "arch: rely on asm-generic/io.h for default
ioremap_* definitions" the ioremap_nocache() symbol has been replaced
with ioremap(). Update the mocked symbol list for nvdimm testing.

Link: https://lore.kernel.org/r/157369090817.2974548.10148423996292973088.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: d092a870

 ("arch: rely on asm-generic/io.h for default ioremap_* definitions")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>