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.