Update .gitignore for arch/i386/boot

With the new setup code, we generate a couple more files
Signed-off-by: NMatthew Wilcox <matthew@wil.cx>
[ .. and do the same for x86-64 - Alexey ]
Acked-by: NAlexey Dobriyan <adobriyan@gmail.com>
Acked-by: NH. Peter Anvin <hpa@zytor.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/i386/boot/.gitignore

 bootsect
 bzImage
 setup
+setup.bin
+setup.elf

arch/x86_64/boot/.gitignore

 bootsect
 bzImage
 setup
+setup.bin
+setup.elf