clk: pistachio: Fix PLL rate calculation in integer mode

.recalc_rate callback for the fractional PLL doesn't take operating
mode into account when calculating PLL rate. This results in
the incorrect PLL rates when PLL is operating in integer mode.

Operating mode of fractional PLL is based on the value of the
fractional divider. Currently it assumes that the PLL will always
be configured in fractional mode which may not be
the case. This may result in the wrong output frequency.

Also vco was calculated based on the current operating mode which
makes no sense because .set_rate is setting operating mode. Instead,
vco should be calculated using PLL settings that are about to be set.

Fixes: 43049b0c("CLK: Pistachio: Add PLL driver")
Cc: <stable@vger.kernel.org> # 4.1
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: Zdenko Pulitika <zdenko.pulitika@imgtec.com>
Signed-off-by: Govindraj Raja <govindraj.raja@imgtec.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>