drm/i915: Support for ns2501-DVO

This patch adds support for the ns2501 DVO, found in some older Fujitsu/Siemens Labtops.
It is in the state of "works for me".
Includes now proper DPMS support. Includes switching between resolutions -
from 640x480 to 1024x768.
Currently assumes that the native display resolution is 1024x768.

The ns2501 seems to be rather critical - if the output PLL is not
running, the chip doesn't seem to be clocked and then doesn't react
on i2c messages. Thus, a quick'n-dirty trick ensures that the DVO
is active before submitting any i2c messages to it. This is
probably to be reviewed.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=17902
Signed-off-by: Thomas Richter <thor@math.tu-berlin.de>
[danvet: fixup whitespace fail.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/Makefile

@@ -40,6 +40,7 @@ i915-y := i915_drv.o i915_dma.o i915_irq.o \
 	  dvo_ivch.o \
 	  dvo_tfp410.o \
 	  dvo_sil164.o \
+	  dvo_ns2501.o \
 	  i915_gem_dmabuf.o
 
 i915-$(CONFIG_COMPAT)   += i915_ioc32.o

drivers/gpu/drm/i915/dvo.h

@@ -140,5 +140,6 @@ extern struct intel_dvo_dev_ops ch7xxx_ops;
 extern struct intel_dvo_dev_ops ivch_ops;
 extern struct intel_dvo_dev_ops tfp410_ops;
 extern struct intel_dvo_dev_ops ch7017_ops;
+extern struct intel_dvo_dev_ops ns2501_ops;
 
 #endif /* _INTEL_DVO_H */