drm/xe: Fix xe_pm_runtime_get_if_in_use documentation

Let's be clear on what it is actually doing and align with
xe_pm_runtime_get_if_active doc style.

Tested-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240522170105.327472-2-rodrigo.vivi@intel.com


Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>