phy: cdns-dphy: Remove leftover code

phy: cdns-dphy: Remove leftover code

The code in cdns-dphy has probably been part of a DSI driver in the
past. Remove DSI defines and variables which are not used or do not
actually do anything. Also rename cdns_dsi_get_dphy_pll_cfg() to
cdns_dphy_get_pll_cfg(), i.e. drop the "dsi", as it's not relevant here.

Reviewed-by: Aradhya Bhatia <aradhya.bhatia@linux.dev>
Tested-by: Parth Pancholi <parth.pancholi@toradex.com>
Acked-by: Vinod Koul <vkoul@kernel.org>
Tested-by: Jayesh Choudhary <j-choudhary@ti.com>
Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://lore.kernel.org/r/20250723-cdns-dphy-hs-clk-rate-fix-v1-2-d4539d44cbe7@ideasonboard.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>