x86: more cleanups in arch/x86/boot/compressed/misc.c

Before:
   total: 7 errors, 8 warnings, 471 lines checked
After:
   total: 5 errors, 5 warnings, 479 lines checked

( the rest cannot be eliminated due to zlib interface cruftiness. )

No code changed:

arch/x86/boot/compressed/misc.o:

   text	   data	    bss	    dec	    hex	filename
  10716	      8	   2152	  12876	   324c	misc.o.before
  10716	      8	   2152	  12876	   324c	misc.o.after

md5:
   2c20c903986a3c9bca44306c6646067e  misc.o.before.asm
   2c20c903986a3c9bca44306c6646067e  misc.o.after.asm

Signed-off-by: Ingo Molnar <mingo@elte.hu>