powerpc/papr_scm: Make some symbols static

The sparse tool complains as follows:

arch/powerpc/platforms/pseries/papr_scm.c:97:1: warning:
 symbol 'papr_nd_regions' was not declared. Should it be static?
arch/powerpc/platforms/pseries/papr_scm.c:98:1: warning:
 symbol 'papr_ndr_lock' was not declared. Should it be static?

Those variables are not used outside of papr_scm.c, so this
commit marks them static.

Fixes: 85343a8d ("powerpc/papr/scm: Add bad memory ranges to nvdimm bad ranges")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200725091949.75234-1-weiyongjun1@huawei.com