msi-wmi: make needlessly global symbols static
msi-wmi: make needlessly global symbols static

backlight is needlessly defined global.
This patch makes the symbol static.

Signed-off-by: Axel Lin <b6ffd6973e972cb999e8e535ab74da7fee0c035f@gmail.com>
Acked-by: Anisse Astier <390294f83260205698f5da093bc86c10504b00c8@astier.eu>
Signed-off-by: Matthew Garrett <4cf8d479716eba9bc68e0146d95320fcb138b96b@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas