video: fbdev: aty: Delete unused variable in radeon_monitor

Fix warning about variable that is asssigned a value but never used.
The variable was indeed never used so delete it.

Keep the call to radeon_probe_i2c_connector() as it may have
side-effects. It is unlikely but I could not verify that is was safe to
drop the call.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linux-fbdev@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20201128224114.1033617-5-sam@ravnborg.org