Pass task_size to vma_area_is_private()

If we want one CRIU binary to work across all AArch64 kernel
configurations, a single task size value cannot be hard coded. Since
vma_area_is_private() is used by both restorer blob code and non
restorer blob code, which must use different variables for recording
the task size, make task_size a function argument and modify the call
sites accordingly. This fixes the following error on AArch64 kernels
with CONFIG_ARM64_64K_PAGES=y.

  pie: Error (pie/restorer.c:929): Can't restore 0x3ffb7e70000 mapping w>
  pie: ith 0xfffffffffffffff7

Signed-off-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>