drm/xe: Fix typo in vram frequency sysfs documentation

Fix function naming and description for xe_vram_freq_sysfs_init
function.

v2: Add fixes tag (Riana)
    Fix review comments (Lucas)

Fixes: 4ae3aeab ("drm/xe: Add vram frequency sysfs attributes")
Signed-off-by: Sujaritha Sundaresan <sujaritha.sundaresan@intel.com>
Reviewed-by: Riana Tauro <riana.tauro@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240117043215.2598677-1-sujaritha.sundaresan@intel.com