Staging: olpc_dcon.c: obsolete use of strict_stroul

As Dan mentioned, dcon_write() will only write u16 values. The
appropriate parts have been changed. As a result of module_param()
not accepting u16 as a valid data type, ushort is used.

Signed-off-by: Valentin Rothberg <valentinrothberg@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>