powerpc/pseries/pmem: Fix a set but not used value

The commit 4c5d87db

 ("powerpc/pseries: PAPR persistent memory
support") set a local variable "count" in dlpar_hp_pmem() but never
use it.

  arch/powerpc/platforms/pseries/pmem.c: In function 'dlpar_hp_pmem':
  arch/powerpc/platforms/pseries/pmem.c:109:6: warning: variable 'count' set but not used

Signed-off-by: Qian Cai <cai@lca.pw>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>