drm/exynos: update phy settings for RB resolutions

This patch updates phy settings of the below
mentioned pixel clocks in Exynos5250 and removes
support for 88.75MHz, for it is not supported.

71 MHz      - 1280x800@60Hz RB
73.25 MHz   - 800x600@120Hz RB
115.5 MHz   - 1024x768@120Hz RB
119 MHz     - 1680x1050@60Hz RB

Signed-off-by: Shirish S <s.shirish@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>