The pci_alloc_irq_vectors() returns a positive number on success.
Hence we have to filter the negative numbers for error condition.
Update the check accordingly.

Fixes: e6951fb78787 ("mfd: intel-lpss: Use PCI APIs instead of dereferencing")
Reported-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20231130143206.1475831-1-andriy.shevchenko@linux.intel.comSigned-off-by: Lee Jones <lee@kernel.org>