drm/ast: Store DRAM clock table in struct ast_device

drm/ast: Store DRAM clock table in struct ast_device

Init the new field dclk_table in struct ast_device to the per-gen
table of DRAM clock parameters. Use the field during modesetting.

The table is static, so a setup is only required once. Removes the
call to IS_AST_GEN() from the atomic commit's code path.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20251007150343.273718-2-tzimmermann@suse.de