PCI/VGA: Pass vga_get_uninterruptible() errors to userspace

PCI/VGA: Pass vga_get_uninterruptible() errors to userspace

If VGA routing cannot be established, vga_get_uninterruptible() returns an
error and does not increment the lock count. Return the error to the
caller.

Return before incrementing uc->io_cnt/mem_cnt so vga_arb_release() won't
call vga_put() when userspace closes the handle.

Signed-off-by: Simon Richter <Simon.Richter@hogyros.de>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260307173538.763188-2-Simon.Richter@hogyros.de