MFC r249041, r249249:

MFC r249041, r249249:

drm and i915: Left-shift iic_msg.slave at creation time

This is required because, in the radeon driver, we can't left-shift in a
central place, like it was done in the i915 driver.

Reviewed by:	kib@, kan@, avg@
Tested by:	kib@, avg@,
		Olivier Cochard-Labbé <olivier@cochard.me>

git-svn-id: svn://svn.freebsd.org/base/stable/9@261625 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f