drm/qxl: remove qxl_log_level global

Smatch reports this issue
qxl_kms.c:36:5: warning: symbol 'qxl_log_level' was not declared. Should it be static?

qxl_log_level is defined qxl_kms.c but unused, so remove.

Signed-off-by: Tom Rix <trix@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220421142054.3751507-1-trix@redhat.com


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>