staging: most: v4l2-aim: optimize list_for_each_entry_safe

As the function get_aim_dev() does not delete elements of the list, the
use of macro list_for_each_entry_safe is not necessary.

This patch replaces the macro list_for_each_entry_safe with the macro
list_for_each_entry.

Signed-off-by: Andrey Shvetsov <andrey.shvetsov@k2l.de>
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>