drm/bochs: Fix DPMS regression

The recent rewrite with the use of regular atomic helpers broke the
DPMS unblanking on X11.  Fix it by moving the call of
bochs_hw_blank(false) from CRTC mode_set_nofb() to atomic_enable().

Fixes: 20371749 ("drm/bochs: Use regular atomic helpers")
Link: https://bugzilla.suse.com/show_bug.cgi?id=1238209


Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20250304134203.20534-1-tiwai@suse.de