fbdev: radeon: fix potential memory leak in radeonfb_pci_register()

fbdev: radeon: fix potential memory leak in radeonfb_pci_register()

The function radeonfb_pci_register() allocates memory for modelist
(by calling radeon_check_modes() which calls fb_add_videomode()).
The memory is appended to info->modelist, but is not freed in subsequent
error paths. Fix this by calling fb_destroy_modelist().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Abdun Nihaal <nihaal@cse.iitm.ac.in>
Signed-off-by: Helge Deller <deller@gmx.de>