drivers: qcom: spm: avoid module usage in non-modular SPM driver

SPM driver provides cpuidle support on some QC SoC's. The functionality
is non-modular and there is no need for module support. Convert module
platform init to builtin platform driver init. The driver functionality
is not affected by this change.

Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>