DRM/i915: Don't delete DPLL Multiplier during DAC init.

The DPLL multipiler is set up in intel_display.c:i9xx_update_pll()
called from i9xx_crtc_mode_set().
There the DPLL multiplier is adjusted so that the SDVO gets a sufficient
bus clock.
When cloning a CRTC between an SDVO driven encoder and the standard
DAC the DAC setup code reseted the multiplier value to 1 thus undoing
the correct setup. There is no need to touch the multiplier in the DAC
setup code: the correct value (i.e. 1 in case no SDVO encoder is used)
is set by i9xx_update_pll() already.
A comment at the code suggested that this code is a left over from the
days when there was no setup for clone modes.

Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>