ANDROID: Fix missing header file for get_cmdline() call

commit ab6f11cf
    uid_sys_stats: log task io with a debug flag
causes on some builds next error:
error: implicit declaration of function 'get_cmdline'
    [-Werror=implicit-function-declaration]

Change-Id: I41adaf5af999b94bac41e3f17a67cfc88400ee31
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>