Staging: android: add __user annotation in binder.c

This fixes the following sparse error
drivers/staging/android/binder.c:1795:36: error: incompatible types in comparison expression (different address spaces)

Change-Id: Icf6b3868442fc3e4f145c8d13de9626abc306cd1
Signed-off-by: Bojan Prtvar <prtvar.b@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: 308fbd8ac0b0078dba29cad027e5b454aac13a6a
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Neeti Desai <neetid@codeaurora.org>
Signed-off-by: Ajay Dudani <adudani@codeaurora.org>