MIPS: VPE loader: Check vmalloc return value in vpe_open
The return value of the vmalloc() call in arch/mips/kernel/vpe.c::vpe_open()
is not checked, so we potentially store a null pointer in v->pbuffer. Add
a check for a null return and then return -ENOMEM in that case.
[Ralf: The check added by Jesper's original patch is where it logically
should be. Adding it eleminated the need for the checks in a few other
places, so I removed them. There still is a zillion of other things that
need to be fixed in this file / API.]