pommed_light: pull fix pending upstream inclusion for -fno-common toolchains
Without the change builds fails on upstream gcc-10 as:
ld: mactel/nv8600mgt_backlight.o:/build/pommed-light/pommed/mactel/nv8600mgt_backlight.c:50: multiple definition of
`lcd_bck_info'; sysfs_backlight.o:/build/pommed-light/pommed/sysfs_backlight.c:124: first defined here