firmware/Makefile: Fix an annoying little error

firmware/synaptics//g3_clr_pr.gen.S: Assembler messages:
firmware/synaptics//g3_clr_pr.gen.S:5: Fatal error: can't extend frag 4294967295 chars
scripts/Makefile.build:343: recipe for target 'firmware/synaptics//g3_clr_pr.gen.o' failed