ANDROID: gki_defconfig: set CONFIG_NR_CPUS=32

Consensus is that CONFIG_NR_CPUS of 32 will deal with the future
products with a moderate engineering margin.  aarch64 only.

Test: confirm value propagates to .config
Bug: 139693734
Bug: 139406736
Bug: 139692860
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Change-Id: I9687d37da254a612947398a45ae56ab01e676562