driver: soc: qcom: Fix function prototype

Replace a #ifdef with a IS_ENABLED() to allow rpmh master stat to be built
as a module.

Fixes: 6d5e0002 ("drivers: soc: qcom: snapshot of sleep drivers for Lahaina")
Change-Id: Ic0dedbad11812a0bd932a9c0099dfb4632842177
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>