drm/amd/display: fix non-kernel-doc comment warnings

Fix kernel-doc warnings for a comment that should not use
kernel-doc notation:

dmub_psr.c:235: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* Set PSR power optimization flags.
dmub_psr.c:235: warning: missing initial short description on line:
* Set PSR power optimization flags.

Fixes: e5dfcd272722 ("drm/amd/display: dc_link_set_psr_allow_active refactoring")
Signed-off-by: Randy Dunlap <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Cc: Robin Chen <[e-mail]>
Cc: Alex Deucher <[e-mail]>
Cc: Anthony Koo <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Harry Wentland <[e-mail]>
Cc: Leo Li <[e-mail]>
Cc: Rodrigo Siqueira <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dce/dmub_psr.c

···
 	dc_dmub_srv_wait_idle(dc->dmub_srv);
 }
 
-/**
+/*
  * Set PSR power optimization flags.
  */
 static void dmub_psr_set_power_opt(struct dmub_psr *dmub, unsigned int power_opt, uint8_t panel_inst)