Revert "drm/ast: Support 1600x900 with 108MHz PCLK"

Revert "drm/ast: Support 1600x900 with 108MHz PCLK"

BugLink: https://bugs.launchpad.net/bugs/1959879
[ Upstream commit 76cea3d95513fe40000d06a3719c4bb6b53275e2 ]

This reverts commit 9bb7b689274b67ecb3641e399e76f84adc627df1.

This caused a regression reported to Red Hat.

Fixes: 9bb7b689274b ("drm/ast: Support 1600x900 with 108MHz PCLK")
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220120040527.552068-1-airlied@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>