drm/i915: fix user irq miss in BSD ring on g4x

commit 5bfa1063a775836a84f97e4df863fc36e1f856ad upstream.

On g4x, user interrupt in BSD ring is missed.
This is because though g4x and ironlake share the same bsd_ring,
their interrupt control interfaces have _two_ differences.

1.different irq enable/disable functions:
On g4x are i915_enable_irq and i915_disable_irq.
On ironlake are ironlake_enable_irq and ironlake_disable_irq.
2.different irq flag:
On g4x user interrupt flag in BSD ring on is I915_BSD_USER_INTERRUPT.
On ironlake is GT_BSD_USER_INTERRUPT

Old bsd_ring_get/put_irq call ring_get_irq and ring_get_irq.
ring_get_irq and ring_put_irq only call ironlake_enable/disable_irq.
So comes the irq miss on g4x.

To fix this, as other rings' code do, conditionally call different
functions(i915_enable/disable_irq and ironlake_enable/disable_irq)
and use different interrupt flags in bsd_ring_get/put_irq.

Signed-off-by: Boqun Feng <boqun.feng@intel.com>
Reviewed-by: Xiang, Haihao <haihao.xiang@intel.com>
Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>