drm/i915/gvt: Propagate vfio_set_irqs_validate_and_prepare() error

drm/i915/gvt: Propagate vfio_set_irqs_validate_and_prepare() error

Return the actual error code from vfio_set_irqs_validate_and_prepare()
instead of always collapsing to -EINVAL. While the helper
currently returns -EINVAL in most cases, passing through the real
error code is more future-proof.

While at it, drop the stray 'intel:' prefix from the error
message.

Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Zhenyu Wang <zhenyuw.linux@gmail.com>
Link: https://lore.kernel.org/r/20251001142336.82089-1-andi.shyti@linux.intel.com