drm: Use pr_cont where appropriate

Using 'printk("\n")' is not preferred anymore and
using printk to continue logging messages now produces
multiple line logging output unless the continuations
use KERN_CONT.

Convert these uses to appropriately use pr_cont or a
single printk where possible.

Miscellanea:

o Use a temporary const char * instead of multiple printks
o Remove trailing space from logging by using a leading space instead

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>