syscall.h: fix doc text for syscall_get_arch()

syscall_get_arch() used to take a task as a argument.  It now uses
current.  Fix the doc text.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

include/asm-generic/syscall.h

@@ -147,7 +147,7 @@ void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
  *
  * Returns the AUDIT_ARCH_* based on the system call convention in use.
  *
- * It's only valid to call this when @task is stopped on entry to a system
+ * It's only valid to call this when current is stopped on entry to a system
  * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP.
  *
  * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must