ANDROID: arm64: fix undeclared 'init_thread_info' error

init_thread_info is deprecated in favour of THREAD_INFO_IN_TASK
related changes, see Change-Id: Ia4769ddcc6fc556e9eb6193d64fc99fe2d9e39ab
("UPSTREAM: arm64: thread_info remove stale items").

Use init_task.thread_info instead, to fix following build error:

arch/arm64/kernel/setup.c: In function 'setup_arch':
arch/arm64/kernel/setup.c:356:2: error: 'init_thread_info' undeclared (first use in this function)
  init_thread_info.ttbr0 = virt_to_phys(empty_zero_page);
  ^

Change-Id: I13bf03211f0d918d388d1436099d286c10a23e5d
Fixes: Change-Id: I85a49f70e13b153b9903851edf56f6531c14e6de
       ("BACKPORT: arm64: Disable TTBR0_EL1 during normal kernel execution")
Fixes: Change-Id: Ia4769ddcc6fc556e9eb6193d64fc99fe2d9e39ab
       ("UPSTREAM: arm64: thread_info remove stale items")
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>