x86/platform/intel-mid: Make 'bt_sfi_data' const

Make this structure const as it is only used during copy operation.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: julia.lawall@lip6.fr
Link: http://lkml.kernel.org/r/1502039720-4471-1-git-send-email-bhumirks@gmail.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>