x86/mm/pageattr: Remove an unused variable in slow_virt_to_phys()

The patch doesn't change any logic.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1429776428-4475-1-git-send-email-decui@microsoft.com


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