Revert "drm/sun4i: add lvds mode_valid function"

Revert "drm/sun4i: add lvds mode_valid function"

The reverted commit broke LVDS output on TBS A711 Tablet. That tablet
has simple-panel node that has fixed pixel clock-frequency that A83T
SoC used in the tablet can't generate exactly.

Requested rate is 52000000 and rounded_rate is calculated as 51857142.
It's close enough for it to work in practice, but with strict check
in the reverted commit, the mode is rejected needlessly in this case.

DT allows to specify a range of values for simple-panel/clock-frequency,
but driver doesn't respect that ATM. Given that TBS A711 is the single
user of sun4i-lvds driver, let's revert that commit for now, until
a better solution for the problem is found.

Also see: https://patchwork.kernel.org/patch/3ed6947/ for relevant
discussion (or search for "[RFC] drm/sun4i: rgb: Add 5% tolerance
to dot clock frequency check").

Fixes: 2208a11d8762 ("drm/sun4i: add lvds mode_valid function")
Reported-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180421045155.15332-1-megous@megous.com
Signed-off-by: Sean Paul <seanpaul@chromium.org>