decompress_unlzma: make "fast" version a bit smaller

It is not slower. In fact it seems a tiny bit faster too.

   text	   data	    bss	    dec	    hex	filename
   2827	      0	      0	   2827	    b0b	decompress_unlzma.o
   2797	      0	      0	   2797	    aed	decompress_unlzma.o

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
1 file changed