exynos_fimg2d_test: fix implicit funciton declaration errors

As one adds WARN_CFLAGS to the build the compiler throws a couple of
lovely error messages. Add the relevant includes to fix them.

  error: implicit declaration of function ‘time’
  error: implicit declaration of function ‘getopt’

Cc: Inki Dae <inki.dae@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Jan Vesely <jan.vesely@rutgers.edu>