Same problem here with an HP 255 G6 laptop with the following GPU details:

Amd radeon R2
GPU name: Beema
Architecture: GCN 2.0 or GCN 1.2
Bus: IGP
UVD 6
Device ID: 98E4

I was able to use suspend before upgrading to 5.0 kernel.

An additional note (I don't know if useful) is that I experience the same
behaviour even before starting X server. I mean, just starting the computer on
tty and then a suspend/resume cycle. At this point everything works; if I try
to start an X server with startx the screen freezes. 

Nothing special in my log different from what has already been posted,