x86/fpu/xsave: Keep __user annotation in casts

Don't remove the __user annotation of the fpstate pointer, but
drop the superfluous void * cast instead.

This fixes the following sparse warnings:

  xsave.c:135:15: warning: cast removes address space of expression
  xsave.c:135:15: warning: incorrect type in argument 1 (different address spaces)
  xsave.c:135:15:    expected void const volatile [noderef] <asn:1>*<noident>
  [...]

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1346621506-30857-6-git-send-email-minipli@googlemail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>