arm64: defconfig: Enable the PSCI CPUidle driver

Enable the PSCI CPUidle driver to replace the functionality
previously provided by the generic ARM CPUidle driver through
CPU operations.

Link: https://lore.kernel.org/r/20190814125239.6270-2-lorenzo.pieralisi@arm.com


Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>