perf: arm_spe: Enable automatic DT loading

When built as a module, the spe driver isn't automatically
loaded on DT systems. Add the MODULE_DEVICE_TABLE entry.

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>