phy: ti-pipe3: Simplify ti_pipe3_dpll_wait_lock implementation

Code simplification. No functional change.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>