clk: qcom: clk-alpha-pll: Fix zonda set_rate failure when PLL is disabled

Currently, clk_zonda_pll_set_rate polls for the PLL to lock even if the
PLL is disabled. However, if the PLL is disabled then LOCK_DET will
never assert and we'll return an error. There is no reason to poll
LOCK_DET if the PLL is already disabled, so skip polling in this case.

Change-Id: Iaea6460f3be58e1591ff49e025017b2c0b7e20ef
Signed-off-by: Mike Tipton <mdtipton@codeaurora.org>