base: soc: Export soc_device_register/unregister APIs

Qcom Socinfo driver can be built as a module, so
export these two APIs.

Tested-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Vaishali Thakkar <vaishali.thakkar@linaro.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>