fbcon: check return value of con2fb_acquire_newinfo()

In the Linux kernel, the following vulnerability has been resolved: fbcon: check return value of con2fb_acquire_newinfo() If fbcon_open() fails when called from con2fb_acquire_newinfo() then info->fbcon_par pointer remains NULL which is later dereferenced. Add check for return value of the function con2fb_acquire_newinfo() to avoid it. Found by Linux Verification Center (linuxtesting.org) with SVACE.