x86/boot: Remove unused 'is_big_kernel' variable

Variable is_big_kernel is defined in arch/x86/boot/tools/build.c but
never used anywhere.

Boris noted that its usage went away 7 years ago, as of:

  5e47c47 ("x86: remove zImage support")

Signed-off-by: Nicolas Iooss <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

arch/x86/boot/tools/build.c

@@ -49,7 +49,6 @@ typedef unsigned int   u32;
 
 /* This must be large enough to hold the entire setup */
 u8 buf[SETUP_SECT_MAX*512];
-int is_big_kernel;
 
 #define PECOFF_RELOC_RESERVE 0x20