Make nvme_pcicfg_read32 set the referenced variable and make
nvme_pcicfg_write32 appear to read it so that the compiler doesn't warn
about unused/uninitialized data.
Change-Id: I4f06c0cca2fc11a8c6c5a60543c1c50a2f6a412d
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>