lib/systems/platforms: remove TI_CPTS override

Forcing the module to be builtin breaks 5.10, which wants to compile it as a
module (probably due to dependencies). There doesn't seem to be a need to have
it builtin anymore, so we can just remove the override.

lib/systems/platforms.nix

@@ -309,9 +309,6 @@ rec {
         SERIAL_8250_EXTENDED y
         SERIAL_8250_SHARE_IRQ y
 
-        # Fix broken sunxi-sid nvmem driver.
-        TI_CPTS y
-
         # Hangs ODROID-XU4
         ARM_BIG_LITTLE_CPUIDLE n