The following build failure occurs when CONFIG_PERF_EVENTS is not set
as generic pmu functions are not visible in that scenario.

|-- s390-randconfig-r044-20220313
|   |-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_migrate_context
|   |-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_register
|   `-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_unregister

Similar build failure in nds32 architecture:
nd_perf.c:(.text+0x21e): undefined reference to `perf_pmu_migrate_context'
nd_perf.c:(.text+0x434): undefined reference to `perf_pmu_register'
nd_perf.c:(.text+0x57c): undefined reference to `perf_pmu_unregister'

Fix this issue by adding check for CONFIG_PERF_EVENTS config option
and disabling the nvdimm perf interface incase this config is not set.

Also remove function declaration of perf_pmu_migrate_context,
perf_pmu_register, perf_pmu_unregister functions from nd.h as these are
common pmu functions which are part of perf_event.h and since we
are disabling nvdimm perf interface incase CONFIG_PERF_EVENTS option
is not set, we not need to declare them in nd.h

Also move the platform_device header file addition part from nd.h to
nd_perf.c and add stub functions for register_nvdimm_pmu and
unregister_nvdimm_pmu functions to handle CONFIG_PERF_EVENTS=n
case.

Fixes: 0fab1ba6 ("drivers/nvdimm: Add perf interface to expose nvdimm performance stats") (Commit id based on libnvdimm-for-next tree)
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Link: https://lore.kernel.org/all/62317124.YBQFU33+s%2FwdvWGj%25lkp@intel.com/Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/20220323164550.109768-1-kjain@linux.ibm.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>