dmraid: rename init script and use FOO_INSTALL_INIT_SYSV

This commit fixes the init script to use the correct
FOO_INSTALL_INIT_SYSV hook.

[Thomas: slightly reword commit log.]

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>