ANDROID: gki_defconfig: set CONFIG_NR_CPUS=32 (x86_64)

Consensus is that CONFIG_NR_CPUS of 32 will deal with the future
products with a moderate engineering margin.  x86_64 only.

Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Test: confirm value propagates to .config
Bug: 139693734
Bug: 139406736
Bug: 139692860
Change-Id: I7c64997a4288be3177a3aac56e89471c9a8b7e20