Update arch/x86/boot/.gitignore with new auto-generated files

Signed-off-by: S.Çağlar Onur <caglar@pardus.org.tr>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/boot/.gitignore

@@ -3,3 +3,5 @@ bzImage
 setup
 setup.bin
 setup.elf
+cpustr.h
+mkcpustr